





i 

1 

'1 

1 

Soils 

AND 

Fertilizers 






Snyder 


■ 




1 






Class 
Book 






Copyright )J?. 



COPYRIGHT DEPOSIT 



SOILS 



AND 



FERTILIZERS 



BY 



HARRY SNYDER, B.S. 

PROFESSOR OF AGRICULTURAL CHEMISTRY, UNIVERSITY OF 

MINNESOTA, AND CHEMIST OF THE MINNESOTA 

EXPERIMENT STATION 



SEIOOND E: D I T I O N 



EASTON, PA. : 
The CHEMICAIv PUBI^ISHING CO. 

1905- 

(all rights reserved) 



UBBARYor ;ONGShS>S 

AUQ 15 jyu5 



O 



¥ 



- '£? 



3 



Copyright, 1899, by Edward Hart. 

1905, " 



PREFACE TO SECOND EDITION 

The first edition of this work was published under 
the title " The Chemistry of Soils and Fertilizers." In 
the revision of the text the subject matter has been 
entirely rewritten, new material has been added, and 
the laboratory practice has been made a more promi- 
nent feature. These additions have changed the scope 
of the book to such an extent as to necessitate a change 
of name. The work as now presented includes all of 
the topics and laboratory practice relating to soils as 
outlined by the Committee on methods of teaching 
Agriculture, appointed by the Association of Agricul- 
tural Colleges and Experiment Stations. The aim of 
the book as presented in the preface to the first edition 
has been kept in view in the preparation of the second 
edition. 

Harry Snyder. 
University of Minnesota, 

coi,i,ege of agricui.ture, 
St. Anthony Park, Minn. 
June /, igo^. 



PREFACE TO FIRST EDITION. 

For several years courses of instruction have been 
given at the University of Minnesota to classes of 
young men who intend to become farmers and who 
desire information that will be of assistance to them 
in their profession. In giving this instruction mimeo- 
graphed notes have been prepared, but the increase 
in the number of students and the volume of notes 
necessitate the publication of this work. In its prep- 
aration, it has been the aim to give, in condensed 
form, the principles of chemistry which have a bear- 
ing upon the conservation of soil fertility and the 
economic use of manures. 



Harry Snyder. 



University of Minnesota, 

COI.I.EGE OF AGRICUIvTURE, 

St. Anthony Park, Minn. 
April 75, iSgg. 



CONTENTS 



INTRODUCTION 

Early uses of manures and explanation of their action by alche- 
mists ; Investigations prior to 1800 : Work of De Saussure, Davy, 
Thaer, and Boussingault ; Liebig's writings and their influence ; 
Investigations of Lawes and Gilbert ; Contributions of other in- 
vestigators ; Agronomy ; Value of soil studies. Pages i-S. 

CHAPTER I 

Physical Properties of Soils. — Chemical and physical properties 
of soils considered ; Weight of soils ; Size of soil particles ; Clay ; 
Sand ; Silt ; Form of soil particles ; Number and arrangement of 
soil particles ; Mechanical analysis of soils ; Crop growth and phys- 
ical properties. Soil types — Potato and truck soils ; Fruit soils ; 
Corn soils ; Medium grass and grain soils ; Wheat soils ; Sandy, 
clay and loam soils. Relation of the soil to water ; Amount of 
water required for crops ; Bottom water ; Capillary water ; Hydro- 
scopic water ; Loss of water by percolation, evaporation and trans- 
piration ; Drainage influence of forest regions ; Influence of culti- 
vation upon the water supply of crops ; Capillary water and culti- 
vation ; Shallow surface cultivation ; Cultivation after rains ; Roll- 
ing ; Sub-soiling ; Fall plowing ; Spring plowing ; Mulching ; Depth 
of plowing ; Permeability of soils ; Fertilizers and their Influence 
upon moisture content of soils ; Farm manures and soil moisture ; 
Relation of soils to heat ; Heat from chemical reactions within the 
soil ; Heat and crop growth ; Organic matter and iron compounds ; 
Color of soils ; Odor and taste of soils ; Power to absorb gases ; 
Relation of soils to electricity ; Importance of physical properties 
of the soil. Pages 9-44. 

CHAPTER II 

Geological Formation and Classification of Soils. — Agricultural 
geology ; Formation of soils ; Action of heat and cold ; Action of 
water ; Glacial action ; Chemical action of water ; Action of air and 
gases ; Action of micro-organism ; Action of vegetation ; Combined 
action of the various agents ; Distribution of soils ; Sedentary and 



vi CONTENTS 

transported soils ; Rocks and minerals from which soils are derived 
as quartz, feldspar, mica, hornblende, zeolites, granite, apatite, 
kaolin ; Disintegration of rocks and minerals ; Value of geological 
study of soils. Pages 45-56. 

CHAPTER III 

Chemical Composition of Soils. — Elements present in soils ; Clas- 
sification of elements ; Combination of elements ; Forms in which 
elements are present in soils; Acid-forming elements, silicon, 
double silicates, carbon, sulphur, chlorine, phosphorus, nitrogen, 
oxygen, hydrogen ; Base-forming elements, aluminum, potassium, 
calcium, magnesium, sodium, iron ; Forms of plant food ; Amount 
of plant food in different forms in various types of soils ; How a 
soil analysis is made ; Value of soil analysis ; Interpretation of the 
results of soil analysis ; Use of dilute acids as solvents in soil anal- 
ysis ; Distribution of plant food in the soil ; Composition of typical 
soils ; "Alkali " soils and their improvement ; Acid soils ; Organic 
compounds of soil ; Sources; Classification; Humus; Humates ; 
Humification ; Humates produced by different kinds of organic 
matter ; Value of humates as plant food, amount of plant food in 
humic forms ; Physical properties of soils influenced by humus ; 
lyoss of humus by forest fires, by prairie fires, by cultivation ; 
Humic acid ; Soils in need of humus ; Soils not in need of humus ; 
Composition of humus from old and new soils ; Influence of differ- 
ent methods of farming upon humus. Pages 57-96. 

CHAPTER IV 

Nitrogen of the Soil and Air, Nitrification and Nitrogenous 
Manures. — Importance of nitrogen as plant food ; Atmospheric 
nitrogen as a source of plant food. Experiments of Boussingault, 
Ville, and Lawes and Gilbert; Result of field trials ; Experiments 
of Hellriegel and Wilfarth and recent investigators ; Composition 
of root nodules ; Amount of nitrogen returned to soil by legumi- 
nous crops and importance to agriculture ; Nitrogenous compounds 
of the soil ; Origin ; Organic nitrogen ; Amount of nitrogen in 
soils ; Removed in crops ; Nitrates and nitrites ; Ammonium com- 
pounds ; Ammonia in rain and drain waters ; Ratio of nitrogen to 
carbon in the soil ; Losses of nitrogen from soils ; Gains of nitrogen 
to soils ; Nitrification ; Former views regarding ; Workings of an 
organism ; Conditions necessary for nitrification ; Influence of cul- 



CONTENTS Vll 

tivation upon these conditions ; Nitrous acid organisms, ammonia- 
producing organisms, denitrification, number and kind of organ- 
isms in soils ; Inoculation of soils with organisms ; Chemical pro- 
ducts produced by organisms ; Losses of nitrogen by fallowing rich 
prairie lands ; Influence of plowing upon nitrification ; Nitrogenous 
manures; Sources; Dried blood, tankage, flesh meal, fish scrap, 
seed residue, and uses of each ; Leather, wool waste and hair ; 
Peat and muck ; Leguminous crops as nitrogenous fertilizers ; Sod- 
ium nitrate, ammonium salts ; Cost and value of nitrogenous fer- 
tilizers. Pages 97-130. 

CHAPTER V 

Farm Manures. — Variable composition of farm manures ; Average 
composition of manures ; Factors which influence composition of 
manures ; Absorbents ; Use of peat and muck as absorbents ; Rela- 
tion of food consumed to manures produced ; Bulky and concen- 
trated foods ; Course of the nitrogen of the food during digestion ; 
Composition of liquid and solid excrements; Manurial value of 
foods; Commercial valuation of manure; Influence of age and 
kind of animal ; Manure from young and old animals ; Cow ma- 
nure ; Horse manure ; Sheep manure ; Hog manure ; Hen manure; 
Mixing manures ; Volatile products from manure ; Human excre- 
ments ; Preservation of manures ; Leaching ; Losses by fermenta- 
tion ; Different kinds of fermentation ; Water necessai^ for fermen- 
tation ; Heat produced during fermentation ; Composting manures; 
Uses of preservatives ; Manure produced in sheds; Value of pro- 
tected manure ; Use of manures ; Direct hauling to field ; Coarse 
manures may be injurious ; Manuring pasture land ; vSmall piles of 
manure in fields objectionable ; Rate of application ; Most suitable 
crops to apply to ; Comparative value of manure and food ; I^asting 
effects of manure ; Comparative value of good and poor manure ; 
Summary of ways in which manures may be beneficial. Pages 

131-159. 

CHAPTER VI 

Fixation. — Fixation a chemical change, examples of ; Due to 
zeolites ; Humus and fixation ; Soils possess different powers of fix- 
ation ; Nitrates do not undergo fixation ; Fixation of ammonia ; 
Fixation may make plant food less available ; Fixation a desirable 
property of soils ; Fixation and the action of manures. Pages 
160-163. 



viii CONTENTS 

CHAPTER VII 

Phosphate Fertilizers. — Importance of phosphorus as plant food ; 
Amount removed in crops ; Amount and source of phosphoric acid 
in soils ; Commercial forms of phosphoric acid ; Phosphate rock ; 
Calcium phosphates ; Reverted phosphoric acid ; Available phos- 
phoric acid ; Manufacture of phosphate fertilizers, acid phosphates, 
superphosphates ; Commercial value of phosphoric acid ; Basic slag 
phosphates ; Guano ; Bones ; Steamed bone ; Dissolved bone ; Bone 
black ; Use of phosphate fertilizers ; How to keep the phosphoric 
acid of the soil available. Pages 164-176. 

CHAPTER VIII 

Potash Fertilizers. — Potassium an essential element; Amount of 
potash removed in crops ; Amount in soils ; Source of soil potash ; 
Commercial forms of potash ; Stassfurt salts, occurrence of ; 
Kainit ; Muriate of potash ; Sulphate of potash ; Other Stassfurt 
salts ; Wood ashes, composition of; Amount of ash in different 
kinds of wood ; Action of ashes on soils ; Leached ashes ; The alka- 
linity of ashes; Coal ashes; Miscellaneous ashes; Commercial 
value of potash ; Use of potash fertilizers ; Joint use of potash 
and lime. Pages 177-186. 

CHAPTER IX 

Lime and Miscellaneous Fertilizers. — Calcium an essential ele- 
ment ; Amount of lime removed in crops ; Amount of lime in soils ; 
Different kinds of lime fertilizers ; Their physical and chemical 
action ; Action of lime upon organic matter and correcting acidity 
of soils ; Lime liberates potash ; Aids nitrification ; Action of land 
plaster on some "alkali " soils ; Quicklime and slaked lime ; Pul- 
verized lime rock ; Marl ; Physical action of lime ; Judicious use of 
lime ; Miscellaneous fertilizers ; Salt and its action on the soil ; 
Magnesium salts ; Soot ; Sea-weed ; Strand plant ash ; Wool wash- 
ings ; Street sweepings. Pages 187-195. 

CHAPTER X 

Commercial Fertilizers. — History of development of industry' ; 
Con)plete fertilizers and amendments ; Variable composition of 
commercial fertilizers ; Preparation of fertilizers ; Inert forms of 
matter in fertilizers ; Inspection of fertilizers ; Mechanical condi- 



CONTENTS IX 

tion of fertilizers ; Forms of nitrogen, phosphoric acid and potash 
in commercial fertilizers; Misleading statements on fertilizer bags ; 
Estimating the value of a fertilizer ; Home mixing ; Fertilizers and 
tillage ; Abuse of commercial fertilizers ; Judicious use of ; Field 
tests ; Preliminary experiments ; Verifying results ; Deficiency of 
nitrogen, phosphoric acid, potash and of two elements ; Import- 
ance of field trials ; Will it pay to use fertilizers? Amount to use 
per acre ; Influence of excessive applications ; Fertilizing special 
crops ; Commercial fertilizers and farm manures. Pages 196-214. 

CHAPTER XI 

Food Requirements of Crops. — Amount of fertility removed by 
crops ; Assimilative powers of crops compared ; Way in which 
plants obtain their food ; Cereal crops, general food requirements ; 
Wheat ; Barley ; Oats; Corn ; Miscellaneous crops ; Flax ; Potatoes ; 
Sugar-beets ; Roots ; Turnips ; Rape ; Buckwheat ; Cotton ; Hops ; 
Hay and grass crops ; Leguminous crops ; Garden crops ; Fruit 
trees ; Lawns, Pages 217-229. 

CHAPTER XII 

Rotation of Crops.— Object of rotating crops ; Principles involved 
in crop rotation ; Deep and shallow rooted crops ; Humus-consum- 
ing and humus-producing crops ; Crop residues ; Nitrogen-consum- 
ing and nitrogen-producing crops ; Rotation and mechanical con- 
dition of soil ; Economic use of soil water ; Rotation and farm 
labor ; Economic use of manures ; Salable crops ; Rotations advan- 
tageous in other ways ; Long- and short-course rotations ; Problems 
in rotations ; Conservation of fertility ; Necessity of manures ; Use 
of crops ; Two systems of farming compared ; Losses of fertility 
with different methods of farming ; Problems on income and outgo 
of fertility from farm. Pages 230-246. 

CHAPTER XIII 

Preparation of Soils for Crops= — Importance of good physical 
condition of seed bed ; Influence of Methods of Plowing upon 
the condition of the seed bed ; Influence of moisture content of 
the soil at the time of plowing ; Influence upon the seed 
bed of pulverizing and fining the soil ; Aeration of seed bed 
necessary ; Preparation of seed bed without plowing ; Mixing 
of sub soil with seed bed ; Cultivation to destroy weeds ; 



X CONTENTS 

Influence of cultivation upon bacterial action ; Inoculation of 
soils ; Cultivation for special crops ; Cultivation to prevent washing 
and gullying of lands ; Bacterial diseases of soils ; Influence of 
crowding of plants in the seed bed ; Selection of crops ; Inherent 
and cumulative fertility of soils ; Balanced soil conditions. Pages 
247-260. 

CHAPTER XIV 

Laboratory Practice.— General directions ; Notebook ; Apparatus 
used in work ; Determination of Hydroscopic moisture of soils ; 
Determination of the capacity of loose soils to absorb water ; Deter- 
mination of Capillary water of soils ; Capillary action of water upon 
soils ; Influence of manure and shallow surface cultivation upon 
moisture content and temperature of soils ; Weight of soils ; Influ- 
ence of color upon the temperature of soils ; Rate of movement of air 
through soils ; Separation of sand, silt and clay ; Sedimentation of 
clay ; Properties of rocks from which many soils are derived ; Form 
and size of soil particles ; Pulverized rock particles ; Reaction of 
soils ; Absorption of gases by soils ; Acid insoluble matter of soils ; 
Acid soluble matter of soils ; Extraction of humus from soils ; Nit- 
rogen in soils ; Testing for nitrates ; Volatilization of ammonium 
salts ; Testing for phosphoric acid ; Preparation of acid phosphate ; 
Solubility of organic nitrogenous compounds in pepsin solution; 
Preparation of fertilizers ; Testing ashes ; Extracting water soluble 
materials from a commercial fertilizer ; Influences of continuous 
cultivation and crop rotation upon the properties of soil ; Sum- 
mary of results with tests of home soil. Pages 261-274. 

References ; Review Questions. Index, pages 275-283, 284-287. 



SOILS AND FERTILIZERS 



INTRODUCTION 

Prior to 1800 but little was known of the sources 
and importance of plant food. Manures had been 
used from the earliest times, and their value was rec- 
ognized, although the fundamental principles under- 
lying their use were not understood. It was believed 
that they acted in some mysterious way. The alche- 
mists had advanced various views regarding their ac- 
tion ; one was that the so-called " spirits " left the de- 
caying manure and entered the plant, producing more 
vigorous growth. As evidence, the worthless charac- 
ter of leached manure was cited. It was thought that 
the spirits had left such manure. The terms ' spirits 
of hartshorn', 'spirits of niter', 'spirits of turpentine ' 
and many others reflect these ideas regarding the com- 
position of matter. 

The alchemists held that one substance, like copper, 
could be changed to another substance, as gold. Plants 
were supposed to be water transmuted in some mys- 
terious way directly into plant tissue. Van Helmont, 
in the seventeenth century, attempted to prove this. 
" He took a large earthen vessel and filled it with 200 
pounds of dried earth. In it he planted a willow 
weighing 5 pounds, which he duly watered with rain 

(I) 



2 SOILS AND FERTILIZERS 

and distilled water. After five years he pulled up the 
willow and it now weighed 169 pounds and 3 ounces." ^ 
He concluded that 164 pounds of roots, bark, leaves, 
and branches had been produced by the direct trans- 
mutation of the water. 

It is evident from the preceding example that any- 
thing like an adequate idea of the growth and compo- 
sition of plant bodies could not be gained until the 
composition of air and water was established. 

The discovery of oxygen by Priestly, in 1774, of 
the composition of water by Cavendish in 1781, and 
of the role which carbon dioxide plays in plant and 
animal life by DeSaussure and others in 1800, form 
the nucleus of our present knowledge regarding the 
sources of matter stored up in plants. It was between 
1760 and 1800 that alchemy lost its grip, because of 
advances in knowledge, and the way was opened for 
the development of modern chemistry. 

The work of DeSaussure, entitled " Recherches sur 
la Vegetation," published in 1804, was the first sys- 
tematic work showing the sources of the compounds 
stored up in plant bodies. He demonstrated, quanti- 
tatively, that the increase in the amount of carbon, 
hydrogen, and oxygen, when plants were exposed to 
sunlight, was at the expense of the carbon dioxide of 
the air, and of the water of the soil. He also main- 
tained that the mineral elements derived from the soil 
were essential for plant growth, and gave the results 
of the analyses of many plant ashes. He believed that 
the nitrogen of the soil was the main source of the 
nitrogen found in plants. These views have since 



INTRODUCTION 3 

been verified by many investigators, and are substan- 
tially those held at the present time regarding the 
fundamental principles of plant growth. They were 
not, however, accepted as conclusive at the time, and 
it was not until nearly half a century later, when 
Boussingault, Liebig, and others repeated the investi- 
gations of DeSaussure, that they were finally accepted 
by chemists and botanists. 

From the time of DeSaussure to 1835, scientific 
experiments relating to plant growth w^ere not actively 
prosecuted, but the scientific facts which had accumu- 
lated were studied, and attempts were made to apply 
the results to actual practice. Among the first to see 
the relation between chemistry and agriculture was 
Sir Humphry Davy. In 1813 he published his " Es- 
sentials of Agricultural Chemistry," which treated of 
the composition of air, soil, manures, and plants, and 
of the influence of light and heat upon plant growth. 
About this same period, Thaer published an important 
work entitled " Principes Raisonnes d' Agriculture." 
Thaer believed that humus determined the fertility of 
the soil, that plants obtained their food mainly from 
humus, and that the carbon compounds of plants were 
produced from the organic carbon compounds of the 
soil. This gave rise to the so-called humus theory, 
which was later shown to be an inadequate idea re- 
garding the source of plant food, and for a time it 
prevented the actual value of humus as a factor of soil 
fertility from being recognized. The writings of Thaer 
were of a most practical nature, and they did much to 
stimulate later investigations. 



4 SOILS AND FERTILIZERS 

About 1830 there was renewed interest in scientific 
investigations relating to agriculture. At this time 
Boussingault, a French investigator, became actively 
engaged in agricultural research. He was the first to 
establish a chemical laboratory upon a farm, and to 
make practical investigations in connection with agri- 
culture. This marks the establishment of the first 
agricultural experiment station. Boussingault's work 
upon the assimilation of the free nitrogen of the air is 
reviewed in Chapter IV. His study of the rotation of 
crops was a valuable contribution to agricultural 
science. He discovered many important facts relating 
to the chemical characteristics of foods, and was the 
first to make a comparative study of the amount of 
nitrogen in different kinds of foods and to determine 
the value of foods on the basis of the nitrogen con- 
tent. His study of the production of saltpeter did 
much to prepare the way for later work on nitrifica- 
tion. The investigations of Boussingault covered a 
variety of subjects relating to plant growth. He re- 
peated and verified much of the earlier work of 
DeSaussure, and also secured many additional facts 
relating to the chemistry of crop growth. As to the 
source of nitrogen in crops, he states that : " The soil 
furnishes the crops with mineral alkaline substances, 
provides them with nitrogen, by ammonia and by 
nitrates, which are formed in the soil at the expense 
of the nitrogenous matters contained in diluvium, 
which is the basis of vegetable earth ; compounds in 
which nitrogen exists in stable combination, only be- 
coming fertilizing by the effect of time." As to the 



INTRODUCTION 5 

absorption of the gaseous nitrogen of the air by vege- 
table earth, he says : " I am not acquainted with a 
single irreproachable observation that establishes it ; 
not only does the earth not absorb gaseous nitrogen, 
but it gives it off." "" 

The investigations of DeSaussure and Boussingault, 
and the writings of Davy, Thaer, Sprengel, and Schiib- 
ler prepared the way for the work and writings of 
Liebig. In 1840 he published "Organic Chemistry 
in its Applications to Agriculture and Physiology." 
Liebig's agricultural investigations were preceded by 
many valuable discoveries in organic chemistry, which 
he applied directly in his interpretations of agricul- 
tural problems. His writings were of a forcible char- 
acter and were extremely argumentative. They pro- 
voked, as he intended, vigorous discussions upon 
agricultural problems. He assailed the humus theory 
of Thaer, and held that humus was not an adequate 
source of the plant's carbon. In the first edition of 
his work he showed that farms from which certain 
products were sold naturally became less productive, 
because of the loss of nitrogen. In a second edition 
he considered that the combined nitrogen of the air 
was sufficient for crop production. He overestimated 
the amount of ammonia in the air, and underestimated 
the value of the nitrogen in soils and manures. A 
study of the composition of plant-ash led him to 
propose the mineral theory of plant nutrition. De- 
Saussure had shown that plants contained certain 
mineral elements, but he did not emphasize their im- 
portance as plant food. Liebig's writings on the com- 



6 SOILS AND FERTILIZERS 

position of plant-ash, and his emphasizing the import- 
ance of supplying crops with mineral food, led to the 
commercial preparation of manures, which in later 
years has developed into the commercial fertilizer in- 
dustry. The work of Liebig was not conducted in 
connection with field experiments. It had, however, a 
most stimulating influence upon investigations in agri- 
cultural chemistry, and to him we owe, in a great de- 
gree, the summarizing of previous disconnected work 
and the mapping out of valuable lines for future in- 
vestigations. 

Liebig's (enthusiasm for agricultural investigations 
may be judged from the following extract : " I shall 
be happy if I succeed in attracting the attention of men 
of science to subjects which so well merit to engage 
their talents and energies. Perfect agriculture is the 
true foundation of trade and industry ; it is the founda- 
tion of the riches of states. But a rational system 
of agriculture cannot be formed without the applica- 
tion of scientific principles, for such a system must be 
based on an exact acquaintance with the means of 
nutrition of vegetables, and with the influence of soils, 
and actions of manures upon them. This knowledge 
we must seek from chemistry, which teaches the mode 
of investigating the composition and of the study of 
the character of the different substances from which 
plants derive their nourishment." 3 

Soon after Liebig's first work appeared, the investi- 
gations at Rothamsted by Sir J. B. Lawes were under- 
taken. The most extensive systematic work in both 
field experiments and laboratory investigations ever 
conducted have been carried on by Lawes and Gilbert 



INTRODUCTION 7 

at Rothamsted, Eng. Dr. Gilbert had previously been 
a pupil at Iviebig, and his becoming associated with 
Sir J. B. Lawes marks the establishment of the second 
experiment station. Many of the Rothamsted experi- 
ments have been continued since 1844, ^^^ results of 
the greatest value to agriculture have been obtained. 
The investigations on the non-assimilation of the at- 
mospheric nitrogen by crops, published in 1861, were 
accepted as conclusive evidence upon this much-vexed 
question. The work on manures, nitrification, the 
nitrogen supply of crops, and on the increase and de- 
crease of the nitrogen of the soil when different crops 
are produced, has had a most important bearing upon 
maintaining the fertility of soils. 

" The general plan of the field experiments has been 
to grow some of the most important crops of rotation, 
each separately, for many years in succession on the 
same land, without manure, with farmyard manure, 
and with a great variety of chemical manures, the 
same kind of manure being, as a rule, applied year after 
year on the same plot. Experiments with different 
manures on the mixed herbage of permanent grass 
land, on the effects of fallow, and on the actual course 
of rotation without manure, and with different manures 
have likewise been made."^ 

In addition to Davy, Thaer, DeSaussure, Bous- 
singault, Liebig, and Lawes and Gilbert, a great 
many others have contributed to our knowledge of 
the properties of soils. The work of Pasteur, while 
it did not directly relate to soils, indirectly had great 
influence upon soil investigations. His researches 
upon fermentation made it possible for Schlosing to 



8 SOILS AND FERTILIZERS 

prove that nitrification was the result of the workings 
of living organisms. These have since been isolated 
and studied by Warington and Winogradsky. 

During recent years the agricultural experiment 
stations of this and other countries have made soils a 
prominent feature of their work ; some of the results 
obtained are noted in the following chapters. Our 
knowledge regarding the chemistry, physics, geology 
and bacteriology of soils is still far from complete, 
but many facts have been discovered which are of the 
greatest value to the practical farmer. The literature 
relating to soils and fertilizers has become very exten- 
sive, and in the classification of agricultural subjects 
for study, soil forms one of the main divisions of 
agronomy. 

In soil investigations it has frequently happened, 
owing to imperfect interpretation of results and to 
the presence of many modifying influences, that the 
conclusions of one investigator appear to be directly 
contradictory to those of another. This is well 
illustrated in the investigations relating to the 
assimilation of free atmospheric nitrogen, where 
seemingly opposite conclusions now form a complete 
theory. 

A scientific study of soils is valuable from an edu- 
cational point of view, as well as because the practical 
knowledge obtained can be utilized in the production 
of crops. In the cultivation of the soil it should be the 
aim to conserve the fertility and to produce as large 
yields as possible of the most valuable crops. This 
can be accomplished only as the result of a thorough 
knowledp^e of soils and fertilizers. 



CHAPTER I 

PHYSICAL PROPERTIES OF SOILS 

1. Soil. — Soil is disintegrated and pulverized rock 
mixed witli animal and vegetable matter. The rock 
particles are of different kinds and sizes, and are in 
various stages of decomposition. If two soils are 
formed from the same kind of rock and differ only in 
the size of the particles, the difference is merely a 
physical one. If, however, one soil is formed largely 
from sandstone, while the other is formed from lime- 
stone, the difference is both physical and chemical. 
Hence it is that soils differ both physically and chem- 
ically. It is difficult to consider the physical proper- 
ties of a soil without also considering the chemical 
properties. The chemical and physical properties, 
when jointly considered, determine largely the agri- 
cultural value of a soil. 

2. Physical Properties Defined. — The physical 
properties of a soil are : 

1. Weight. 

2. Color. 

■ 3. Size, form, and arrangement of the soil particles. 

4. The relation of the soil to water, heat, and cold. 

5. Odor and taste. 

6. The relation of the soil to electricity. 

3. Weight. — Soils differ in weight according to the 
composition and size of the particles. Fine sandy 
soils weigh heaviest, while peaty soils are lightest in 



lO SOILS AND FERTILIZKRS 

weight. But when saturated with water, a cubic foot 
of peaty soil weighs more than a cubic foot of sandy 
soil. Clay soils weigh less per cubic foot than sandy 
soils. The larger the amount of organic matter in a 
soil the less the weight. Pasture land, for example, 
weighs less per cubic foot than arable land. Weight 
is an important property to consider when the total 
amounts of plant food in two soils are compared. A 
peaty soil containing i per cent, of nitrogen and 
weighing 30 pounds per cubic foot has less total nitro- 
gen than a soil containing 0.40 per cent, of nitrogen 
and weighing 80 pounds per cubic foot. 

The weight of soils per cubic foot is approximately 
as follows : 5 

Pounds. 

Clay soil 70 to 75 

Fine sandy soil 95 to 1 10 

Loam soil 75 to 90 

Peaty soil 25 to 60 

Average prairie soil 75 

Uncultivated prairie soil 65 

Figures for the weight per cubic foot and specific 
gravity of soils are on the basis of the dry soil. When 
taken from the field the weight per cubic foot varies 
with the amount of water present. 

The volume of a soil varies with the conditions to 
which it has been subjected. Usually about 50 per 
cent, of the volume is air space. A cubic foot of soil 
from a field which has been well cultivated weighs 
less than from a field where the soil has been com- 
pacted. Hence it is that soils have both a real and 
an apparent specific gravity. The apparent specific; 



SIZE OF SOIIv PARTICI^KS II 

gravity of a soil is sometimes less than half of the real 
specific gravity. The specific gravity of different soils 
as given by Shoen is as follows : ^ 

specific gravity. 

Clay soil 2.65 

Sandy soil 2.67 

Fine soil 2.71 

Humus soil 2.53 

4, Size of Soil Particles.— The size of soil particles 
varies from those hardly distinguishable with the 
microscope to coarse rock fragments. The size of the 
particles determines the character of the soil as sandy, 
clay, or loam. The term ' fine earth ' is used to 
designate that part of a soil which passes through a 
sieve with holes 0.5 mm. (0.02 inch) in diameter. 
Coarse sand particles and rock fragments which fail 
to pass through the sieve are called skeleton. The 
amounts of fine earth and skeleton are variable. Ara- 
ble soils, in general, contain from 5 to 20 per cent, of 
skeleton. 

The fine earth is composed of six grades of soil 
particles. The names and sizes are as follows : 

Millimeters. Inches. 

Medium sand 0.5 to 0.25 0.02 to o.oi 

Fine sand 0.25 to o.i o.oi to 0.004 

Very fine sand o.i to 0.05 0.004 to 0.002 

Silt : 0.05 to O.OI 0.002 to 0.0004 

Fine silt o.oi to 0.005 0.0004 to 0.0002 

Clay 0.005 and less 0.0002 and less 

Soils are mechanical mixtures of various-sized par- 
ticles. In most soils there is a predominance of one 
grade, as clay in heavy clay soils, and medium sand 
in" sandy soils. No soil, however, is composed entirely 



12 SOILS AND FERTII^IZERS 

of one grade. The clay particles are exceedingly 
small ; it would take 5000 of the larger ones, if laid 
in a line with the edges touching, to measure an inch, 
while it would take but 50 of the larger medium sand 
particles to measure an inch. 

5. Clay. — The term clay used physically denotes 
those soil particles less than 0.005 mm. (0.0002 inch) 
in diameter, without regard to chemical composition. 
As used in a physical sense clay may be silica, feld- 
spar, limestone, mica, kaolin, or any other rock or 
mineral which has been pulverized until the particles 
are less than 0.005 mm. in diameter. Chemically, 
however, the term clay is restricted to one material, 
as will be explained in another part of the work. The 
physical properties of clay are well known. It has the 
power of absorbing a large amount of water, and will 
remain suspended in water for a long time. The 
roiled appearance of many streams and lakes is due to 
the presence of suspended clay particles. The amount 
in agricultural soils may range from 3 to 50 per cent. 
Clay soils, if worked when too wet, become puddled ; 
then percolation cannot take place, and the accumu- 
lated surface water must be removed by the slow 
process of evaporation. 

6. Silt. — Silt particles are, in size, between sand 
and clay. Many of the western prairie subsoils, clay- 
like in nature, are composed mainly of silt. The silt 
imparts characteristics intermediate to sand and clay. 
While a clay soil is nearly impervious to water, and 
when wet works with difficulty, a silt soil is more per- 
meable, but is not as open and porous as a sandy soil. 



SAND 



I3 



When a soil containing large amounts of clay and silt 
is treated with water, the silt settles slowly, while 
the clay remains in suspension. The fine deposit in 
ditches and drains, where the water moves slowly, is 
mainly silt. 

7. Sand. — There are three grades of sand. The 
characteristics, as permeability and non-cohesion of 

/ 




Fig. I.- Medium sand X i50- Fig. 2. Fine sand X 150- Fig. 3. 
Very fine sand X I50- Fig- 4- Silt X 325. Fig. 5. Fine silt X 
325. Fig. 6. Clay X 325- 

particles, are so well known that they do not require 
discussion. A soil composed entirely of sand would 
have little, if any, agricultural value. Sandy soils 
usually contain from 5 to 15 per cent, of clay and 
silt. The relative sizes of sand, silt, and clay are given 
in the illustration. 



14 SOILS AND FERTILIZERS 

8. Form of Soil Particles, — Soil particles are ex- 
tremely varied in form. When examined with the 
microscope they show the same diversity as is observed 
in larger stones. In some soils the particles are spher- 
ical, while in others they are angular. The shape of 
the particles is determined by the way in which the 
soil has been formed, and also by the nature of the 
rock from which it was produced. 

The form and arrangement of the particles are im- 
portant factors to consider in dealing with the water 
content of soils. In the wheat lands of the Red River 
Valley of the North, the particles are small and spher- 
ical, being formed largely from limestone rock, while 
the subsoil of the western prairie regions is composed 
largely of angular silt particles, which are intermingled 
with clay, forming a mass containing only a minimum 
of inter soil spaces. The silt particles being angular 
and embedded in the clay, the soil has more the char- 
acter of clay than of silt. While these two soils are 
unlike in physical composition, the form and arrange- 
ment of the particles give each nearly the same water- 
holding power. Two soils may have the same mechan- 
ical composition and yet possess materially different 
physical properties because of a difference in the form 
and arrangement of the soil particles. In some soils 
lo per cent, of clay is of more agricultural value than 
in other soils. Ten per cent, of clay associated with 
60 or 70 per cent, of silt makes a good grain soil, 
while 10 per cent, of clay associated largely with sand 
makes a soil poorly suited to grain culture. 

The classification of the soil particles into sand, silt. 



SEPARATING soil. PARTICLES 1 5 

and clay is purely an arbitrary one. Various authors 
use these terms in different ways, and when compar- 
ing soils reported in different works, one may avoid 
confusion by omitting the names and noting only the 
sizes of the particles. A division has recently been 
suggested by Hopkins^ in which the square root of ten 
is taken as the constant ratio between the grades of 
soil particles. 

9. Number of Particles per Gram of Soil.— It has 
been estimated that a gram of soil contains from 
2,000,000,000 to 20,000,000,000 soil particles ; soils 
which contain less than 1,700,000,000 are unproduc- 
tive. The number of particles in a given volume of 
soil varies with their size .and form. According to 
Whitney^ the number of particles per gram of differ- 
ent soil types is as follows : 

Karly truck 1,955,000,000* 

Truck and small fruit 3,955,000,000 

Tobacco 6,786,000,000 

Wheat 10,228,000,000 

Grass and wheat 14,735,000,000 

L/imestone 19,638,000,000 

Assuming that the particles are all spheres, it is es- 
timated that in a cubic foot of soil a surface area of 
from two to three and one-half acres is presented to 
the action of the roots. 

1 . Methods Employed in Separating Soil Particles . 
— Sieves with circular holes 0.5, 0.25 and o.i mm. 
are employed for the purpose of separating the three 
coarser grades of sand. The sieve a^ o. 5 mm. size, is con- 

* Figures below sixth place omitted and cyphers substituted. 



i6 



SOIIvS AND FKRTIUZERS 



nected with the filtering flask c by means of the tube 
b^ and the flask is connected at point d with a suction- 
pump. Ten grams of soil, after soft pestling with 
boiling water, are placed in the sieve. Water is passed 
through until the washings are clear. All particles 
larger than 0.5 mm. remain in the sieve and, after dry- 
ing and igniting, are weighed. The contents of flask ^, 
containing the particles less than 0.5 mm. are then 
passed through a sieve having holes 0.25 mm. in 
diameter. Finally a o.io mm. diameter sieve is used. 

The fine sand and silt are separated by gravity. The 
fine sand with some silt and clay are read- 
ily deposited and the water containing 
the suspended clay is decanted into a 
second glass vessel. The residue is treated 
with more water and allowed to settle ; 
this operation is repeated until the micro- 
scope shows the soil particles to be nearly 
all of one grade. The separation of silt 
and clay is facilitated 
by the use of a centrifu- 
gaL9 

The clay is obtained Figs. 8 and 9. 
by evaporating an aliquot portion of the washings or 
by determining the total per cent, of the other grades 
of particles and the volatile matter and subtracting 
the sum from 100. This is the modified Osborne sed- 
imentation method. ^° 

Hilgard's elutriator" is a valuable apparatus for 
separating the soil particles. 





SOIL TYPES 

11. Crop Growth and Physical Properties. — The 

preference of certain crops for particular kinds of soil, 
as wheat for a clay subsoil, potatoes for a sandy soil, 
and corn for a silt soil, is due mainly to the peculiari- 
ties of the crop in requiring definite amounts of water, 
and a certain temperature for growth. These, condi- 
tions are met by the soil being composed of various 
grades of particles which enable a certain amount of 
water to be retained, and the soil to properly respond 
to the influences of heat and cold. In considering 
soil types, it should be remembered that there are so 
many conditions influencing crop growth that the 
crop-producing power cannot always be determined by 
a mechanical analysis of the soil. The following 
types have been found to hold true in a large number 
of cases under average conditions, but they do not 
represent what might be true of a case under special 
conditions. For example, a sandy soil of good fer- 
tility in which the bottom water is only a few feet 
from the surface, may produce larger grain crops than 
a clay soil in which the bottom water is at a greater 
depth. In judging the character of a soil, special 
conditions must always be taken into consideration. 
* In discussing the following soil types, a normal supply 
of plant food and an average rainfall are assumed in 
all cases. 

12. Potato and Early Truck Soils.— The better 
types of potato soils are those which contain about 60 
percent, of medium sand, 20 to 25 per cent, of silt, and 

(2) 



1 8 SOILS AND FERTILIZERS 

about 5 per cent, of clay. Soils of this nature when 
supplied with about 3 per cent, of organic matter will 
contain from 5 to 12 per cent, of water. The best 
conditions for crop growth exist when the soil con- 
tains about 8 per cent, of water. In a sandy soil, 
vegetation may reduce the water to a much lower 
point than in a clay soil. On account of sandy soil 
giving up its water so readily to growing crops nearly 
all is available, while on heavy clay, crops show the 
want of water when the soil contains from 7 to 8 per 
cent, because the clay holds the water so tenaciously. 
When potatoes are grown on soils where there is an 
abnormal amount of water the crop is slow in matur- 
ing. For early truck purposes in northern latitudes, 
sandy soils are the most suitable because they warm 
up more readily, and the absence of an abnormal 
amount of water results in early maturity. Excellent 
crops of potatoes are grown on many of the silt soils 
of the west which have a materially different com- 
position from the type given. A soil may have all 
of the requisites physically for the production of good 
potato and truck crops, and still be unproductive on 
account of unbalanced chemical composition or lack 
of plant food. 

13. General Truck and Fruit Soils. —For fruit grow- 
ing and general truck purposes the soil should contain * 
more clay and less sand than for early truck farming. 
Soils containing from 10 to 15 per cent, of clay and 
not more than 50 per cent, of sand are best suited for 
growing small fruits. Such soils will retain from 10 
to 18 per cent, of water. There is a noticeable differ- 



MKDIUM GRASS AND GRAIN SOILS 1 9 

ence as to the adaptability of different kinds of fruit 
to different soils. Some fruits thrive on clay land, 
provided the proper cultivation and treatment are 
given. There is as much diversity of soil required for 
producing different fruit crops as for the production of 
different farm crops. As a rule, however, a silt soil is 
most capable of being adapted to the various conditions 
required by fruit crops. 

14. Corn Soils. — The strongest types of corn soils 
are those which contain from 40 to 45 per cent, of 
medium and fine sand and about 15 per cent, of clay. 
Corn lands should contain about 15 per cent, of avail- 
able water. Heavy clays require more cultivation and 
produce corn crops which mature later than those 
grown on soils not so close in texture. Many corn 
soils contain less sand and clay, but more silt than the 
figures given. If a soil contains a high per cent, of 
neutral organic matter, good corn crops may be pro- 
duced where there is less than 12 per cent, of clay. 
Soils containing a high per cent, of sand are usually 
too deficient in available water to produce a good corn 
crop. On the other hand, heavy clay soils are slow in 
warming up and are not suited to corn culture. 

The best types of corn soils have the necessary 
mechanical composition for the production of good 
crops of sorghum, cotton, flax, and sugar-beets. How- 
ever, the amount of available plant food required for 
each crop is not the same. The western prairie soils, 
which produce most of the corn raised in the United 
States, are composed largely of silt. 

15. Medium Grass and Grain Soils. — For the pro- 



20 SOILS AND FERTILIZERS 

duction of grass and grain a larger amount of water 
is required than for corn. The yield is determined 
largely by the amount of water which the soil con- 
tains. For an average rainfall of about 30 inches, 
good grass and grain soils should contain about 15 per 
cent, of clay and 60 per cent, of silt. Such a soil 
ordinarily holds from 18 to 20 per cent, of water. 
Many grass and grain soils have less silt and more 
clay. A soil composed of about 30 per cent, each of 
fine sand, silt, and clay, would also be suitable, me- 
chanically, for general grain production. There are 
a number of different types of grass and grain soils, 
with different proportional amounts of sand, silt, and 
clay. Silt soils, however, form the larger part of the 
grain soils of the United States. 

16. Wheat Soils. — For wheat production, soils of 
closer texture are required than for other small grains. 
There are three classes of wheat soils. The first (i 
in Fig. 10) contains from 30 to 50 per cent, of clay 
particles, these being mostly disintegrated limestone. 
The soil of the Red River Valley of the North belongs 
to the first class. The surface soil contains from 8 to 
12 per cent, of vegetable matter and the subsoil about 
25 per cent, of limestone in a very fine state of division. 
For the production of wheat, the subsoil should con- 
tain 20 per cent, of water. A crop can, however, be 
produced with less water, but a smaller yield is ob- 
tained. 

The second type of wheat soil (2 in Fig. 10) con- 
tains less clay and more silt. Many prairie subsoils 
which produce good crops of wheat contain about 20 



WHEAT SOII.S 



21 



per cent, of sand. 50 per cent, of silt, and from 20 to 
30 per cent, of clay. Soils of this class when well 
stocked with moisture in the spring are capable of 
producing good crops of wheat, but are not able to 
withstand drought so well as soils of the first class ; 
during wet seasons, however, they produce larger 
yields than heavier clay soils. 

12 3 4 



C/^y 




1.' <".!«. >.»<'«>;.«. 




f/ne J 



Fig. 10. Soil types. 

I. Heavy wheat soil. 2. Average wheat soil. 3. Medium wheat 
and grain soil. 4. Corn soil. 

To the third class of wheat soils (3 in Fig. 10) be- 
long those which are composed mainly of silt, contain- 
ing usually 75 per cent, and from 10 to 15 per cent, of 
clay. The high per cent, of fine silt gives the soil 
clay-like properties. Soils of this class are adapted to 
a great variety of crops. For the production of wheat 



22 SOILS AND FERTILIZERS 

on silt soils, it is essential that a good supply of 
organic matter be kept in the soil so as to bind 
the soil particles. The special peculiarities of the 
different grain crops as to soil requirements are con- 
sidered in connection with the food requirements of 
crops. 

17. Sandy, Clay, and Loam Soils. — In ordinary 
agricultural literature, the term ' sandy,' ' clay,' or 
' loam ' is used to designate the prevailing character of 
the soil. Sandy soils usually contain 90 per cent, or 
more of silica or chemically pure sand. The term 
light sandy soil is sometimes used to indicate that 
the soil is easily worked, while the term heavy clay 
means that the soil offers great resistance to cultiva- 
tion. Many soils which are clay-like in character are 
not composed very largely of clay. They are sub- 
soils in the western states which have clay -like char- 
acteristics but contain only about 15 percent, of clay, 
the larger part of the soil being silt. A loam soil is a 
mixture of sand and clay ; if clay predominates the 
soil is a clay loam, while if sand predominates it is a 
sandy loam. 

RELATION OF THE SOIL TO WATER 

18. Amount of Water Required by Crops. — Ex- 
periments have shown that it takes from 275 to 375 
pounds of water to produce a pound of dry matter in 
a grain crop. In order to produce an average acre of 
wheat, 350 tons of water are needed. The amount of 
water required for the production of an average acre 
of various crops is as follows : '^ . 



BOTTOM WATER 23 

* Average amount. Minimum amount. 

Tons water. Tons water. 

Clover . . 400 310 

Potatoes 400 325 

Wheat 350 300 

Oats 375 300 

Peas 375 300 

Corn 300 

Grapes 375 

Sunflowers^ 6000 

The rainfall during the time of growth is frequently 
less than the amount of water required for the pro- 
duction of a crop. One inch of rainfall is equal to 
about 90 tons per acre. An average rainfall of 2 
inches per month during the three months of crop 
growth is equivalent to only 540 tons of water per 
acre, a large part of which is lost by evaporation. 
Hence it is that the rainfall during an average grow- 
ing season is less than the amount of water required 
to produce crops, and hence the water stored up in the 
subsoil must be drawn upon to a considerable extent. 
Inasmuch as the soil's reserve supply of water is such 
an important factor in crop production, it follows that 
the capacity of the subsoil for storing and supplying 
water as needed is a matter of much importance, par- 
ticularly since the power of the soil for absorbing 
and retaining water may be influenced by cultivation 
and manuring. Before discussing the influence of 
cultivation upon the soil water, the forms in which it 
is present in the- soil should be studied. Water is 
present in soils in three forms : (i) bottom water, (2) 
capillary water, and (3) hydroscopic water. 

19. Bottom Water is water which stands in the soil 



24 SOILS AND FERTILIZERS 

at a general level, and fills all the spaces between the 
soil particles. Its distance from the surface can be 
told in a general way by the depth of surface wells. 
Bottom water is of service to growing crops when it is 
at such a depth that it can be brought to the plant 
roots by capillarity, but when too near the surface so 
that the roots are immersed, very poor conditions for 
crop growth exist. When the bottom water can be 
brought within reach of the roots by capillarity, a crop 
has an almost inexhaustible supply. In many soils 
known as old lake bottoms, such conditions exist. 




Fig, II. Water films surrounding soil particles. 

20. Capillary Water. — The water held in the 
minute spaces above the bottom water is known as the 
capillary water. The capillary spaces of the soil are 
the small spaces between the soil particles in which 
water is held by surface-tension ; that is, the force 
acting between the soil and the water is greater than 
the force of gravity. If a series of glass tubes of dif- 
ferent diameters be placed in water it will be observed 
that in the smaller tubes water rises much higher than 
in the larger. The water rises in all of the tubes 
until a point is reached where the force of gravity is 
equal to the force of surface-tension. In the smaller 
tubes surface-tension is greater than the force of 



CAPII^LARY WATER 



25 



gravity, and the water is drawn up into the tube. In 
the larger tubes the surface-tension is less and water 
is raised only a short distance. There are present in 
the soil many spaces which are capable of taking 
up water in the same way as the small glass tubes. 
The height to which water can be raised by capillarity 
depends upon the size and arrangement of the soil 
particles. Water may be raised by capillarity to a 
height of several feet. Ordinarily, however, the capil- 
lary action of water is confined to a few feet. The 



Fig. 12. Comparative height to which water rises in glass tubes. 

arrangement of the soil particles influences greatly the 
capillary power of the soil. Usually from 30 to 60 per 
cent, of the bulk of a soil is air space ; by compacting, 
the air spaces are decreased ; by stirring, the air spaces 
are increased. In soils of a close texture, as heavy 
clays, an increase in air spaces results in an increase of 
capillary spaces and of water-holding capacity, while 
in other soils, as coarse sandy soils, increasing the air 
spaces decreases the capillary spaces and the water- 
holding capacity. The best conditions for crop pro- 
duction exist when the soil contains water to the extent 
of about 40 per cent, of its total capacity of saturation. 



26 SOILS AND FERTILIZERS 

21. Hydroscopic Water, — By hydroscopic water is 
meant the water content of the soil absorbed from the 
atmosphere. The air which occupies the non-capillary 
spaces of the soil is charged with moisture in propor- 
tion to the water in the soil. Under normal condi- 
tions the soil atmosphere is nearly saturated. When 
soils have exhausted their capillary water, the water 
in the soil atmosphere is correspondingly reduced. 
The available supply in other forms being exhausted, 
the hydroscopic water cannot contribute to plant 
growth unless the soil is supplied with hydroscopic 
water from heavy fogs. 

22. Loss of Water by Percolation. — Whenever a 
soil becomes saturated, percolation or a downward 
movement of the water begins. The extent to which 
losses by percolation may occur depends upon the 
character of the soil and the amount of rainfall. 
When soils are covered with vegetation, the losses by 
percolation are less than from barren fields. In all 
soils which have only a limited number of capillary 
spaces and a large number of non-capillary spaces, the 
amount of water w^hich can be held above the bottom 
water is small. From such soils the losses by perco- 
lation are greater than from soils which have a larger 
number of capillary spaces, and a smaller number of 
non-capillary spaces. In coarse sandy soils many of 
the spaces are too large to be capillary. 

If all of the water which falls on some soils could be 
retained and not carried beyond the reach of crops by 
percolation, there would be an ample supply for agri- 
cultural purposes. To prevent losses by percolation, 



LOSS OF WATER BY EVAPORATION 27 

the texture of the soil may be changed by cultivation 
and by the use of manures. If the soil is of very fine 
texture, as a heavy clay, percolation is slow, and before 
the water has time to sink into the soil, evaporation 
begins ; with good cultivation, the water is able to 
penetrate to a depth beyond the immediate influence 
of evaporation. Compacting an open porous soil by 
rolling, checks rapid percolation and prevents the 
water from being carried beyond the reach of plant 
roots. In order to prevent excessive losses by perco- 
lation, the management must be varied to suit the re- 
quirements of different soils. In regions of heavy 
rainfall and mild winters the losses of both water and 
plant food by percolation are often large. 

23. Loss of Water by Evaporation. — The factors 
which influence evaporation are temperature, humid- 
ity, and rate of movement of the air. When the air 
contains but little moisture and is heated and moving 
rapidly, the most favorable conditions for evaporation 
exist. In semiarid regions the losses of water by 
evaporation are much greater than by percolation. 
The dry air comes in contact with the soil, the soil 
atmosphere gives up its water, which has been taken 
from the soil, and, unless checked by cultivation, the 
subsoil water is brought to the surface by capil- 
larity and lost. In porous soils, a greater free- 
dom of movement of the air is possible, which 
increases the rate of evaporation. When the sur- 
face of the soil is covered with a layer of finely 
pulverized earth, or with a mulch, excessive losses 
by evaporation cannot take place, because a material 



28 SOIIvS AND FERTILIZERS 

of different texture is interposed between the soil and 
the air. 

24. Loss of Water by Transpiration. — Losses of 
water may also occur from the leaves of plants by the 
process known as transpiration. Helriegel observed 
that during some years 100 pounds more water were 
required to produce a pound of dry matter than in 
other years, because of the difference in the amount of 
water lost by transpiration. The loss of water by 
evaporation can be controlled by cultivation, but the 
loss by transpiration can be only indirectly influenced. 
Hot, dry winds m.ay cause crops to wilt because the 
water lost by transpiration exceeds the amount which 
the plant takes from the soil. 

25. Drainage. — Good drainage is essential in order 
to properly regulate the water supply. An excessive 
amount of water in the soil is equally as injurious as 
a scant amount. If the water which falls on the land 
is allowed to flow over the surface and is not retained 
in the soil, there is not sufficient reserve water for 
crop growth. The object of good drainage is to store 
as much water as possible in the subsoil and to pre- 
vent surface accumulation and loss. Good drainage 
is accomplished by thorough cultivation, and in re- 
gions of heavy rainfall, by tile drainage. Well-drained 
land is warmer in the spring, has a larger reserv^e 
store of water, and is in better condition for crop 
o^rowth. The drainag^e of wet and low lands forms an 
important feature of rural engineering. Many swampy 
lands are highly productive when properly drained. 



CAPILLARITY INFLUENCED BY CULTIVATION 29 

The reclamation of such lands is briefly considered in 
Chapter III. 

26. Influence of Forest Regions. — The deforesting 
of large areas near the sources of rivers has an injurious 
influence upon the moisture content of adjoining farm 
lands. By cutting over and leaving barren large tracts, 
less water is retained in the soil. Near forest regions 
the air has a higher moisture content, due to the 
water given off by evaporation. Farm lands adjacent 
to deforested districts lose water more rapidly by 
evaporation, because the air is so much drier. In 
Section 24 it was stated that losses of water by trans- 
piration could be indirectly influenced. This can be 
accomplished by retaining our forests. 

Good drainage is necessary not only for individual 
farms, but also for an entire community. Good stor- 
age capacity in the form of forest lands, for the surplus 
water which accumulates near the sources of large 
rivers is also a necessity to agriculture. 

The three ways in which crops are deprived of 
water are by (i) percolation, (2) evaporation, and (3) 
transpiration. With proper methods of cultivation 
losses by percolation and evaporation may be controlled, 
and losses by transpiration may be reduced. 

INFLUENCE OF CULTIVATION UPON THE WATER SUPPLY 
OF CROPS 

27. Capillarity Influenced by Cultivation. — The 

capillarity of the soil can be influenced by different 
methods of cultivation, as rolling and subsoiling, deep 
plowing and shallow surface cultivation. The method 
of cultivation which a soil should receive in order to 



30 



SOILS AND FERTILIZERS 



secure the best water supply for crops must vary with 
the rainfall, the nature of the soil, and the crop to be 
produced. It frequently happens that the annual 
rainfall is sufficient to produce good crops, but is too 
unevenly distributed, and hence is not all utilized to 
the best advantage. It is possible, to a great extent, 
to vary the cultivation so as to conserve the moisture 
of the soil and meet the requirements of crops. 

28. Shallow Surface Cultivation.— When shallow 
surface cultivation is practiced, the capillary spaces 




Fig. 13. Soil with surface cultivation. 

near the surface are destroyed and the direct connec- 
tion of the subsoil water with the surface is broken, 
a layer of finely pulverized earth covers the surface, 
and the soil particles have been disturbed so there 
is not that close contact which enables the water to 
pass from particle to particle. When evaporation takes 
place there is a movement of the subsoil water to the 
surface, but if the surface is covered with a layer of 
fine earth of different texture, the subsoil water can- 
not readily pass through such a medium, and evapora- 
tion is checked. Hence shallow surface cultivation 
conserves the soil moisture. 

The means by which surface cultivation is accom- 



SHALLOW SURFACE CULTIVATION 3 1 

published must, of necessity, vary with the nature of the 
soil. If a harrow is used, the pulverization should be 
complete. If a disk is used, the teeth should be set at 
an angle, and not perpendicularly, so as to prevent, as 
suggested by King,'^ the formation of hard ridges 
which hasten evaporation. When the disk is set at an 
angle, a layer of soil is completely cut off, and the 
capillary connection with the subsoil is broken. Sur- 
face cultivation should be from two to three inches 




Fig. 14. Soil without surface cultivation. 

deep, and the finer the condition in which the surface 
soil is left the better. 

Shallow surface cultivation is an effectual means of 
conserving soil moisture. It can be practiced in con- 
nection with deep plowing, shallow plowing, subsoil- 
ing, or rolling ; in fact, it can be combined with any 
method of treating the land. Shallow surface cultiva- 
tion does not mean that the soil should not be pre- 
viously well prepared by thorough cultivation. The 
following example shows the extent to which shallow 
surface cultivation may conserve the soil water. ^^ 

Per cent, of water in cornfield. 

With shallow sur- Without shallow 
face cultivation. surface cultivation. 

Soil, depth 3 to 9 inches 14.12 8.02 

Soil, depth 9 to 15 inches 17.21 12.38 



32 SOII.S AND FERTILIZERS 

29. Cultivation After a Rain. — When evaporation 
takes place immediately after a rain, not only is there 
a loss of the water which has fallen, but there may 
also be a loss of the subsoil water by translocation, if 
nothing be done to prevent.'^ The following example 
shows the extent to which the subsoil water may be 
brought to the surface. '^ 

Per cent, of water. 

Surface soil. Subsoil. 

I to 3 inches. 6 to 12 inches. 

Before the shower 9.77 18.22 

After the shower 22.11 16.70 

The rainfall was sufficient to have raised the water 
content of the surface soil to 20.77 per cent. The 
subsoil showed a loss of 1.52 per cent, while the sur- 
face soil showed a gain of 1.34 per cent, in addition to 
the water received from the shower. If evaporation 
begins before the equilibrium is reestablished, there is 
lost, not only the water from the shower, but also the 
water which has been translocated from the subsoil to 
the surface. Hence the importance of shallow surface 
cultivation immediately after a rain. 

When a subsoil contains a liberal supply of water, 
and the surface soil a minimum amount, there is after 
a shower a movement of the subsoil water to the sur- 
face. The soil particles at the surface are surrounded 
with films of water which thicken at the expense of 
the subsoil water. Surface-tension is the cause of this 
movement of the water to the surface, and under the 
conditions stated it is temporarily greater than the 
force of gravity. 

A hard thin crust should never be allowed to form 



SUBSOII.ING 33, 

after a rain, because it hastens losses by evaporation, 
while a soil mulch formed by surface cultivation has 
the opposite effect. 

30. Rolling. — The use of heavy rollers for com- 
pacting the soil is beneficial in a dry season on a soil 
containing large' proportions of sand and silt. Rolling 
the land compacts the soil and improves the capillary 
condition, enabling more of the subsoil water to be 
brought to the surface. Experiments have shown 
that when land is rolled the amount of water in the 
surface soil is increased. This increase is, however, 
at the expense of the subsoil water. ^3 Unless rolled 
land receives surface cultivation, excessive losses by 
evaporation, due to improved capillarity, may result. 
The use of the roller on heavy clay land during a wet 
season results unfavorably. In some localities rolling 
and subsequent surface cultivation are not admissible 
on account of the drifting of the soil, caused by heavy 
winds. 

31. Subsoiling. — By subsoiling is meant pulveri- 
zing of the soil below the furrow slice. This is 
accomplished with the subsoil plow, which simply 
loosens the soil without bringing the subsoil to the 
surface. The object of subsoiling is to enable the 
land to retain, near the surface, more of the rainfall. 
Heavy clay lands are sometimes improved by occasional 
subsoiling, but its continued practice is not desirable. 
For orcharding and fruit-growing, it is frequently re- 
sorted to, but is not beneficial on soils containing 
large amounts of sand and silt. Rolling and subsoil- 
ing are directly opposite in effect. Soils which are 

(3) 



,34 SOILS AND FERTILIZERS 

improved by rolling are not improved by snbsoiling. 
The additional expense involved should be considered 
when snbsoiling is to be resorted to. Experiments 
have not as yet been sufficiently decisive to indicate 
all cf the conditions most favorable for this practice. 

32. Fall Plowing followed by surface cultivation 
conserves the soil water, by checking evaporation and 
leaving the land in better condition to retain moisture. 
If conditions allow, fall plowing should be followed 
by surface cultivation. In some localities heavy winds 
prevent this from being practiced. Evaporation may 
take place from unplowed land during the fall, and in 
the spring the soil contain appreciably less water than 
plowed land. By fall plowing it is possible to carry 
over a water balance in the soil from one year to the 
next. 

33. Spring Plowing. — When land is plowed late in 
the spring there has been a loss of water by evapora- 
tion, and the soil has not been able to store up as 
much of the rain and snow as if fall plowing had 
been practiced. ^^ D^y soil is plowed under and moist 
soil brought to the surface. If surface cultivation 
does not follow, this moisture is readily lost by evapo- 
ration, good capillary connection of the surface soil 
and subsoil is not obtained, and the furrow slice soon 
becomes dry. 

Per cent, of water ini-^ 

April 25th. Fall plowed Spring plowed 

land. land. 

From 2 to 6 inches 24.7 22.4 

" 6 to 12 " 26.6 24.1 

" 12 to 18 " 28.8 26.5 

Average difference 2.37 per cent. 



DEPTH OF PI^OWING 35 

Surface cultivation should immediately follow both 
spring and fall plowing. 

34. Mulching. — The use of well-rotted manure or 
straw, spread over the surface as a mulch, prevents 
evaporation. In forests the leaves form a mulch 
which is an important factor in maintaining the water 
supply. In order that a mulch be effectual, it must 
be compacted, — a loose pile of straw is not a mulch. 
In reclaiming lands gullied by water, mulching is 
very beneficial." A light mulch may also be used to 
encourage the growth of grass on a refractory hillside. 
When land is mulched, evaporation is checked. Sur- 
face cultivation and mulching may be advantageously 
combined. ^4 

Per cent, of water in 

Mulched straw- 
berry patch. Unmulched. 

Soil 2 to 5 inches 18.12 11. 17 

" 6 to 12 " 22.18 18.14 

'* 12 to 18 " 24.31 21.11 

35. Depth of Plowing. — The depth to which a soil 
should be plowed in order to give the best results must, 
of necessity, vary with the conditions. Deep plowing 
of sandy land is not advisable, particularly in the 
spring. On clay land deeper plowing should be the 
rule. The longer a soil is cultivated the deeper and 
more thorough should be the cultivation. While 
shallow plowing is admissible on new prairie land, 
deeper cultivation should be practiced when the land 
has been cropped for a series of years. Also, the 
depth of plowing should be regulated by the season. 
In the prairie regions, and in the northwestern part of 



36 SOILS AND FERTILIZERS 

the United States, shallow plowing is more generally 
practiced than in the eastern states. Deep plowing in 
the fall gives better results than in the spring. It is 
not a wise plan to plow to the same depth every year. 
Prof. Roberts saysV^ "If plowing is continued at one 
depth for several seasons, the pressure of the imple- 
ment and the trampling of the horses in time solidify 
the bottom of the furrow, but if the plowing is shallow 
in the spring and deep in summer and fall, the objec- 
tional hard pan will be largely prevented." 

In regions of scant rainfall deep plowing of silt soils 
should be done only at intervals of three or five years. 
With an average rainfall, deep plowing should be the 
rule on soils of close texture. The depth of plowing 
should be varied to meet the requirements of the crop, 
of the soil and the amount of rainfall. 

36. Permeability of Soils. — The rapidity with 
which water sinks into the soil after a rain depends 
upon the nature of the soil, and upon the cultivation 
which it has received. Shallow surface cultivation 
leaves the soil in good condition to absorb water. 
When the surface is hard and dry a large per cent, of 
the water which falls on rolling land is lost by sur- 
face drainage. Soils of close texture which contain 
but few non-capillary spaces, offer the greatest resist- 
ance to the downward movement of water. 

A soil is permeable when it is of such a texture that 
it does not allow the water to accumulate and clog 
the non-capillary spaces. Cultivation may change 
the tilth of even a clay soil to such an extent as to 
render it permeable. Deep plowing increases per- 



FARM MANURES 37 

nieability. In regions of heavy rains increased per- 
meability is very desirable for good crop production 
on heavy clays. Sandy and loamy soils have a high 
degree of permeability, and it is not necessary that it 
should be increased. 

37, Fertilizers. — When water contains dissolved 
salts, it is more susceptible to the influence of surface- 
tension, and is more readily brought to the surface of 




Fig. 15. Sandy soil without manure. 

the soil. In commercial fertilizers soluble salts are 
present. The beneficial effects of commercial fertili- 
zers upon the moisture content of soils are liable to 
be over-estimated, because the fertilizer undergoes fix- 
ation when applied, and does not remain in a soluble 
condition. Fertilizers containing soluble salts exercise 
a favorable influence upon the moisture content of 
soils, but the extent of this influence has never been 
determined under field conditions. 

3*8. Farm Manures. — Well-prepared farm manures 
exercise a beneficial effect upon the moisture content of 
soils. When well-rotted manure is worked into a soil, 
the coarse soil particles and masses are bound together, 



38 



SOILS AND FERTII.IZERS 



and the non-capillary spaces are made capillary. Free 
circulation of the air, which increases evaporation, 
is prevented when a sandy soil is manured. When 




Fig. 1 6. Sandy soil with manure. 

silt and sandy soils are manured they are capable of 
retaining more water, as shown by the following ex- 
ample : ^4 



Fine sandy 
soil. 
Per cent. 



Capacity for holding water . 



25 



95 per cent, fine 

sandy soil 

and 5 per 

cent, manure. 

Per cent. 

42 



The manure enables the soil to retain more water 
near the surface and prevents losses by percolation. 
The difference in moisture content between manured 
and unmanured land is particularly noticeable in a 
dry season. ^4 



Sandy soil 

well manured. 

Water. 

Per cent. 



Soil one to six inches 10.50 



Sandy soil 
unmanured. 

Water. 

Per cent. 

8.10 



Coarse leached manure may have just the opposite 
effect by producing an open and porous condition of 
the soil. 



RELATION OF THE SOIL TO HEAT 

39. The Sources of Heat in soils are (i) solar 
heat, and (2) heat resulting from chemical action. 
Solar heat is the main source for crop production. 
The action of heat upon soils has been studied exten- 
sively by Schiibler. The amount of heat a soil is 
capable of absorbing depends upon its texture and 
moisture content. All dark-colored soils have a 
greater power for absorbing heat than light-colored 
ones. From Schiibler's experiments it appears that 
when dry, there may be as great a difference as S° C, 
between light- and dark-colored soils. When one set 
of soils was covered with a thin white coat of mag- 
nesia, and another set with lampblack, and exposed 
under like conditions, the temperatures were :^ 

White coating. Black coating. 

Sand ^ 43 50 

Gypsum 43 5i 

Humus • 42 49 

Clay 41 48 

I/Oam 42 50 

The presence of water in the soil modifies the powder 
for absorbing heat. A sandy soil retains about 1 2 per 
cent, of water, while a humus soil retains 35 per cent. 
The additional amount of water in the humus soil 
causes the soil temperature to be lower than that of 
the sandy soil. While the humus soil absorbs more 
heat than the sandy soil, the heat is used up in warm- 
ing the water. A sandy soil readily warms up in the 
spring on account of the relatively srnalj amount of 
water which it contains. 



40 SOILS AND FERTILIZERS 

The specific heat of a soil is the amount of heat re- 
quired to raise a given weight i° C, as compared with 
the heat required to raise the same weight of water i°. 
The specific heat of soils ranges from 0.2 to 0.4. 

The effect of drainage upon soil temperature is 
marked. The surface of well-drained land is usually 
several degrees warmer than that of poorly drained 
land. Water being a poor conductor of heat it follows 
that soils which are saturated are slow to warm up in 
the spring. At a depth of 2 or 3 feet there is not such 
a marked difference in the temperature of wet and dry 
soils. It is to be observed that with proper systems of 
drainage the surplus water is removed from the sur- 
face soil and stored up in the subsoil for the future use 
of the crop, and at the same time the temperature of the 
surface soil is raised, thus improving the conditions for 
crop growth. The relation of drainage to the proper 
supply of water and temperature for crop growth is a 
matter which generally receives too little consideration 
in field practice. 

40. Heat from Chemical Reactions within the 
Soil. — Heat also results from the slow oxidation of 
the organic matter of the soil. When organic matter 
decomposes, it produces heat. A load of manure, when 
it rots in the soil, gives off the same amount of heat as 
if it were burned. Manured land is usually 1° or 2° 
warmer in the spring than unmanured land ; this is 
due to the oxidation of the manure. In an acre of rich 
prairie soil it has been estimated that the amount of or- 
ganic matter which undergoes oxidation produces as 
much heat annually as would be produced from a ton 



ORGANIC MATTER AND IRON COMPOUNDS 4I 

of coal.^7 In well-drained and well-manured land, the 
additional heat is an important factor for stimulating 
crop growth, particularly in a cold, backward spring. 
The production of heat from manure is utilized in 
the case of hotbeds where well-rotted manure is covered 
with soil ; this results in raising the temperature of the 
soil. When soils are well manured, heat is retained 
more effectually. In case of early frosts, crops on 
well-manured land will often escape. 

4. Relation of Heat to Crop Growth. — All plant 
life is directly dependent upon solar heat as the source 
of energy for the production of plant tissue. The 
heat of the sun is the main force at the plant's dis- 
posal for decomposing water and carbon dioxide and 
for producing starch, cellulose, and other compounds- 
The growth of crops is the result of the transformation 
of solar heat into chemical energy which is stored up 
in the plant. When the plant is used for fuel or for 
food the quantity of heat produced by complete oxida- 
tion is equal to the amount of heat required for the 
formation of the plant's tissues. 

COLOR OF SOILS 

42. Organic Matter and Iron Compounds. — The 

principal materials which impart color to soils are or- 
ganic matter and iron compounds. Soils containing 
large amounts of organic matter are dark-colored. 
A Tinion of the decaying organic matter with the 
mineral matter of the soil produces compounds brown 
or black in color. When moist, many soils are darker 
than when dry, and soils in which the organic matter 



42 SOILS AND FERTILIZERS 

has been kept up by the use of manures are darker 
than unmanured soils/^ When rich, black, prairie 
soils lose their organic matter through improper 
methods of cultivation, or when the organic matter 
(humus) is extracted in chemical analysis the soils 
become light-colored. 

The red color of soils is imparted by ferric oxide, 
the yellow, by smaller amounts of the same material. 
A greenish tinge is supposed to be due to the pres- 
ence of ferrous compounds, such soils being so close in 
texture as to prevent the oxidizing action of the air. 
Color may serve, to a slight extent, as an index of fer- 
tility. Black and yellow soils are, as a rule, the most 
productive. The main reason why black soils are so 
generally fertile is because they contain a higher per 
cent, of nitrogen. Black soils are occasionally unpro- 
ductive because of the presence of compounds injurious 
to vegetation. 

43. Odor and Taste of Soils.— Soils containing 
liberal amounts of organic matter have characteristic 
odors. The odoriferous properties of a soil are due to 
the presence of aromatic bodies produced by the de- 
composition of organic matter. In cultivated soils 
these bodies have a neutral reaction. Poorly drained 
peaty soils give off volatile acid compounds when 
dried. The amount of aromatic compounds in soils 
is very small. 

The taste of soils varies with the chemical compo- 
sition. Poorly drained peaty soils usually have a 
slightly sour taste, due to the presence of organic 



RKI.ATION OF SOILS TO ELECTRICITY 43 

acids. Alkaline soils have variable tastes according to 
the prevailing alkaline compound. The taste of a 
soil frequently reveals a fault, as acidity or alkalinity. 

44. Power of Soils to Absorb Gases. — All soils pos- 
sess, to a variable extent, the power of absorbing 
gases. When decomposing animal or vegetable matter 
is mixed with soil, the gaseous products given off are 
absorbed. Absorption is the result of both chemical 
and physical action. The chemical changes which 
occur, as the fixation of ammonia, are considered in 
the chapter on fixation. The organic matter of the 
soil is the principal agent in the physical absorption of 
gases ; peat has the power of absorbing large amounts. 
This action is similar to that of a charcoal filter in 
removing noxious gases from water. 

45. Relation of Soils to Electricity. — There is al- 
ways a certain amount of electricity in both the soil 
and the air. The part which it takes in plant growth 
is not well understood. The action of a strong cur- 
rent upon the soil undoubtedly results in a change in 
chemical composition, but in order to change the 
composition of the soil so as to render the unavailable 
plant food available, would require a current destruc- 
tive to vegetation. When plants are subjected to too 
strong a current of electricity, they wilt and have all 
of the after-effects of frost. A feeble current has either 
an indifferent or a slightly beneficial effect upon crop 
growth. The slightly beneficial action is not sufficient, 
however, to warrant its use as yet in general crop pro- 
duction on account of cost. The action of a weak 



44 - SOILS AND FERTILIZERS 

current of electricity is undoubtedly physiological 
rather than chemical, unless it be in the slighty favor- 
able influence which it exerts upon nitrification. The 
electrical conductivity of soils has been taken by Whit- 
ney as the basis for the determination of moisture ; '9 
the conductivity of a soil, however, is dependent 
largely upon the nature and amount of dissolved salts. 

46. Importance of the Physical Study of Soils, — 

From what has been said regarding the physical prop- 
erties of soils it is evident that such a study will give 
much valuable information regarding their probable 
agricultural value. While the physical properties 
should always be taken into consideration, they should 
not form the sole basis for judging the character of a 
soil, because two soils from the same locality frequently 
have the same general physical composition and still 
have entirely different crop-producing powers, due to 
differences in chemical composition and amounts of 
available plant food. 

Attempts have been made to over-estimate the value 
of the physical properties of soils and to explain nearly 
all soil phenomena on the basis of soil physics. Im- 
portant as are the physical properties of a soil, it can- 
not be said that they are of more importance than the 
chemical or other properties. In fact the four sciences, 
chemistry, physics, geology, and bacteriology, are all 
closely connected and each contributes its part to our 
knowledge of soils. 



CHAPTER II 

GEOLOGICAL FORMATION AND CLASSIFICATION OF SOILS 

47. Agricultural Geology. — The geological study 
of a soil concerns itself with the past history of that 
soil, the materials out of which it has been produced, 
together with the agencies which have taken a part in 
its formation and distribution. Geologically, soils are 
classified according to the period in the earth's history 
when formed, and also according to the agencies 
which have distributed them. The principles of soil 
formation and soil distribution should be understood, 
because they have such an important bearing upon 
soil fertility. Agricultural geology is of itself a 
separate branch of agricultural science. In this work, 
only a few of the topics which are of most importance 
in agriculture are treated and only in a general way. 

48. Formation of Soils. — Geologists state that the 
surface of the earth was at one time solid rock. It is 
now held that soils have been formed from rock by 
the joint action of the various agents : (1) heat and 
cold, (2) water, (3) gases, (4) micro-organisms and 
vegetable life. One of the best evidences that soil is 
derived from rock is that there are frequently found 
in fields pieces of rock which are actually rotten, and, 
when crushed, closely resemble the prevailing soil of 
the field. This is particularly true of clay soils where 
fragments of disintegrated feldspar are found which, 
when crushed, resemble the soil in which the feldspar 



46 SOILS AND FERTILIZERS 

was embedded. The process of soil formation is a slow 
one and the various agents have been at work for an 
almost unlimited period. 

49. Action of Heat and Cold. — The cooling of the 
earth's surface, followed by a contraction in volume, 
resulted in the formation of fissures which exposed a 
larger area to the action of other agents. The un- 
equal cooling of the rocks caused a partial separation 
of the different minerals of which the rocks were com- 
posed, resulting in the formation of smaller rock par- 
ticles from the larger rock masses. This is well 
illustrated by the familiar splitting and crumbling of 
stones when heated. Shaler estimates that a variation 
of 150° F. will make a difference of 1 inch in the 
length of a granite ledge 100 feet long. As a result of 
changes in temperature there is a lessening of the 
cohesion of the rock particles. The action of frost 
also is favorable to soil formation. The freezino- of 

o 

water in rock crevices results in breaking up the lock 
masses, forming smaller bodies. The force exerted by 
water when it freezes is sufffcient to rend large rocks. 

50. Physical Action of Water. — Water acts upon 
soils both chemically and physically. It is the most 
important agent that has taken a part in soil forma- 
tion. The surface of rocks has been worn away by 
moving water and in many cases deep ravines and 
caiions have been formed. This is called erosion. 
The pulverized rock, being carried along by the water 
and deposited under favorable conditions, forms 
alluvial soil. This physical action of water is illus- 



GLACIAL ACTION 47 

trated in the workings of large rivers where the 
pulverized rock is deposited along the river and at its 
mouth. lyarge areas of the soil in valleys and river 
bottoms have been formed in this way, and in most 
cases these soils are of high fertility. The action of 
water is not alone confined to forming soils along 
water courses, but is equally prominent in the forma- 
tion of soils remote from streams or lakes, as in the 
case of soils deposited by glaciers. 

51. Glacial Action. — At one time in the earth's 
history, the ice-fields of polar regions covered much 
larger areas than at present.^° Changes of climate 
caused a recession of the ice fields, and resulted in the 
movement of large bodies of ice, carrying along rocks 
and frozen soil. The movement and pressure of the 
ice pulverized the rock and produced soil. This 
action is well illustrated at the present time where 
mountains rise above the snow line, and the ice and 
snow melting at the base are replaced by ice and 
snow from farther up, moving down the side of the 
mountain and carrying along crushed stones and soil. 
When the glacier receded, stranded ice masses were 
distributed over the land. These melted slowly and 
by their grinding action hollowed out places which 
finally became lakes. The numerous lakes at the 
source of the Mississippi River and in central Min- 
nesota are supposed to have been formed by glacial 
action. The terminal of a glacier is called a moraine 
and is covered with large boulders which have not 
been disintegrated. The course of a glacier is fre- 
quently traced by the markings or scratches of the 



48 SOILS AND FERTILIZERS 

mass on rock ledges. In glacial soils, the rocks are 
never angular, but are smooth because of the grinding 
action during transportation. The area of glacial soils 
in the northern portion of the United States is quite 
large. These soils are, as a rule, fertile because of 
the pulverization and mixing of a great variety of 
rock. 

52. Chemical Action of Water. — The chemical 
action of water has been an important factor in soil 
formation. While nearly all rocks are practically in- 
soluble in water there is always some material dis- 
solved, evidenced by the fact that all spring- water 
contains dissolved mineral matter. When charged 
with carbon dioxide and other gases, water acts as a 
solvent upon rocks. It converts many oxides, as fer- 
rous oxide, into hydroxides. The chemical action of 
water may produce new compounds more soluble or 
readily disintegrated, as deposits of clay, which have 
been formed from feldspar rock by the chemical and 
physical action of water. When rocks disintegrate^ 
chemical changes often occur ; the addition of water 
or hydration of the molecule, particularly of the sili- 
cates, is ofie of the most important chemical changes. 
Water takes as prominent a part in the decay of rocks 
as in the decay of vegetable matter. Limestone is 
quite readily disintegrated by water. Dissolved min- 
erals produce many chemical changes in both rocks 
and soils. The chemical action of fertilizers known 
as fixation can take place only in the presence of 
water. In fact, water is necessary for nearly all of the 



ACTION OF VEGETATION 49 

chemical reactions in the soil which result in render- 
ing plant food available. 

53. Action of Air and Gases. — In the disintegra- 
tion of materials to form soil, air takes a prominent 
but less important part than water. By the aid of 
oxygen, carbon dioxide, and other gases and vapors 
in the air, rock disintegration is hastened. The action 
of oxygen changes the lower oxides to higher forms. 
All rock contains more or less oxygen in chemical 
combination. The carbon dioxide of the air under 
some conditions favors the formation of carbonates. 
The disintegrating action of air, moisture, and frost is 
illustrated in the case of building stones which in 
time crumble and form a powder. This is called 
weathering. Many of the benefits of cultivation are 
due to aeration of the soil. 

54. Action of Micro-organisms. — Micro-organisms, 
found on the surface and in the crevices of rocks, and 
in decaying vegetable matter, are active agents in 
bringing about rock decay. The nitrifying organisms 
have taken an important part in rendering soils fer- 
tile, and these with others have aided in soil forma- 
tion. Some of the organisms found on the surface of 
rocks are capable of producing carbonaceous matter 
out of the carbon dioxide and other compounds of 
the air.^^ This action results in adding vegetable 
matter to the soil. 

55. Action of Vegetation. — Some of the lower 
forms of plants as lichens do not require soil for 
growth, but are capable of living on the bare surface 

(4) 



50 SOILS AND FERTILIZERS 

of rocks, obtaining food from the air, and leaving a 
certain amount of vegetable matter which undergoes 
decay and is incorporated with the rock particles, pre- 
paring the way for higher orders of plants which take 
their food from the soil. When this vegetable matter 
decays, it enters into chemical combination with the 
pulverized rock, forming humates.'^ The disinte- 
grating action of plant roots and vegetable matter 
upon rocks has been an important factor in soil forma- 
tion. The action of vegetable remains in soil produc. 
tion is discussed in Chapter III. 

56. Combined Action of the Various Agents. — In 

the decay of rocks the various agents named — water 
acting mechanically and chemically, heat and cold, 
air, micro-organisms, and vegetation — have been act- 
ing jointly, and have produced more rapid disinte- 
gration than if each agent were acting separately. 
Wind also has been an important factor in the pro- 
duction and modification of soils. The denuding 
effects of heavy wind storms are well known. Large 
areas of wind-formed soils are found in some coun- 
tries. Sand dunes are transported by winds and often 
their subjugation by soil-binding plants is necessary 
in order to prevent their encroaching upon valuable 
farm lands and inundating villages. Soils formed by 
the action of winds are called aeolian soils. 
DISTRIBUTION OF SOILS 

57. Sedentary and Transported Soils, — The place 
which a soil occupies is not necessarily the place 
where it was produced ; that is, a soil may be pro- 



COMPOSITION OF ROCK 5 1 

duced in one locality and transported to another. 
Soils are either sedentary or transported. Sedentary 
soils are those which occupy the original position 
where they were formed. They usually have but 
little depth before rock surface is reached. The stones 
in such soils, except where modified by weathering, 
have sharp angles because they have not been ground 
by transportation. In the southern part of the United 
States, east of the Mississippi River, there are large 
areas of sedentary soils as ferrogenous clays in an ad- 
vanced state of decay. 

Transported soils are those which have been formed 
in one locality and carried by various agents as glaciers, 
rivers and winds to other localities, the angles of stones 
in these soils having been ground off during transpor- 
tation. Transported soils are divided into classes ac- 
cording to the ways in which they have been formed; 
as, drift soils produced by glaciers, alluvial soils formed 
by rivers and deposited by lakes, aeolian soils formed 
by winds, and colluvial soils formed of rocks and 
debris from mountain sides. 

In some localities volcanic soils are found. They 
are extremely varied in texture and composition ; 
some are very fertile and contain liberal amounts of 
alkaline salts and phosphates, while others contain so 
little plant food that they are sterile. 

ROCKS AND MINERALS FROM WHICH SOILS ARE FORMED 

58, Composition of Rocks. — Rocks are composed of 
either a single mineral or of a combination of minerals. 
Most of the common minerals are definite chemical 



52 SOILS AND FERTII.IZERS 

compounds and have a variable range of composition, 
due to the fact that one element or compound may be 
partially or entirely replaced by another. Most rocks 
from which soils have been produced contain minerals 
as feldspar, mica, hornblende, and quartz. 

59. Quartz and Feldspar. — Quartz is the principal 
constituent of many rock formations. Pure quartz is 
silicic anhydride (SiOJ. White sand is nearly pure 
quartz or silica. Silica enters into combination with 
many elements, forming a large number of minerals. 
A soil formed from pure quartz would be sterile. 

Feldspar is composed of silica, alumina, and potash 
or soda. Lime may also be present, and replace a 
part or nearly all of the soda. If the mineral contains 
soda as the alkaline constituent it is known as albite, 
or if mainly potash it is called potash feldspar or 
orthoclase. 

The members of the feldspar group are insoluble in 
acids and before disintegration takes place are not 
capable of supplying plant food. Potash feldspar 
contains from 12 to 15 per cent, of potash, none of 
which is of value as plant food. When feldspar 
undergoes disintegration it produces kaolin or clay. 
A soil formed from feldspar is usually well-stocked 
with potash. 

Orthoclase, AlKSigOg Potash feldspar, 

Albite, AlNaSigOg Sodium feldspar. 

60. Hornblende. — The hornblende and augite groups 
are formed by the union of magnesium, calcium, iron, 
and manganese, with silica. There are none of the 



ZEOLITES 53 

members of the alkali family in hornblende. The 
augites are double silicates of iron, manganese, cal- 
cium, and magnesium. Quite frequently, phosphoric 
acid is present in chemical combination with the iron. 
The members of this group are readily distinguished 
by their color which is black, brown, or brownish 
green. The hornblendes are insoluble in acids, hence 
unavailable as plant food, and when disintegrated do 
not as a rule form very fertile soils. 

6i, Mica, — Mica is quite complex in composition, 
is an abundant mineral, and is composed of silica, 
iron, alumina, manganese, calcium, magnesium, and 
potassium. Mica is a polysilicate. The color may 
be white, brown, black, or bluish green owing either 
to the absence of iron, or to its presence in various 
amounts. The chief physical characteristic of the 
members of this group is the ease with which they are 
split into thin layers. It is to be observed that the 
mica group contains all of the elements of both feld- 
spar and hornblende. 

Soils formed from disintegrated micia are usually 
fertile, owing to the variety of essential elements 
present. Frequently small pieces of undecomposed 
mica are found in soils. 

62. Zeolites. — The zeolites are a large group of 
secondary or derivative minerals formed from disin- 
tegrated rock. They are polysilicates containing 
alumina and members of the alkali and lime families, 
and all contain water held in chemical combination. 
They are partially soluble in dilute hydrochloric acid 



54 SOILS AND FERTILIZERS 

and belong to the group of compounds which are 
capable, to a certain extent, of becoming available as 
plant food. In color, they are white, gray, or red. 
Zeolites are quite abundant in clay and are an import- 
ant factor in soil fertility. It is this group of hydrated 
silicates which takes such an important part in the 
process of fixation. The zeolites, when disintegrated, 
particularly by glacial action, form very fertile soils. 

63. Granite is composed of quartz, feldspar, and 
mica. It is a very hard rock and slow to disintegrate. 
The different shades of granite depend upon the pro- 
portion in which the various minerals are present. 
Inasmuch as granite contains so many minerals it 
usually follows that thoroughly disintegrated granite 
soil is very fertile. Pure powdered granite before 
undergoing disintegration furnishes no plant food. 
After weathering, the plant food gradually becomes 
available. Gneiss belongs to the granite series but 
differs from true granite in containing a larger amount 
of mica. Mica schist contains a larger amount of 
mica than gneiss. 

64. Apatite or Phosphate Rock. — Apatite is com- 
posed mainly of phosphate of lime, Ca„(PO )^, together 
with small amounts of other compounds as fluorides 
and chlorides. This mineral is generally of a green 
or yellow color. It is present in many soils and is of 
little value as plant food unless associated wnth or 
ganic matter or some soluble salts. 

65. Kaolin is chemically pure clay and is formed by 
the disintegration of feldspar. When feldspar is de- 



DISINTEGRATION OF ROCKS AND MINERALS 55 

composed and is acted upon by water the potash is re- 
moved and water of hydration is taken up, forming 
the product kaolin, which is hydrated silicate of alu- 
mina, Al (SiO ) .H^O. Impure varieties of clay are 
colored red and yellow on account of the presence of 
iron and other impurities. Pure kaolin is white, is 
insoluble in acids, and is incapable of supplying any 
nourisment to plants. Clay soils are fertile on account 
of the other minerals and organic matter mixed with 
the clay and are usually well-stocked with potash be- 
cause of the incomplete removal of the potash from 
the disintegrated feldspar. It is to be observed that 
the term clay used chemically means aluminum sili- 
cate, while physically it is any substance, the particles 
of which are less than 0.005 ^^^- ^^^ diameter. 

66. Disintegration of Rocks and Minerals. — In ad- 
dition to the rocks and minerals which have been 
mentioned, there are many others that contribute to 
soil formation as limestone which is calcium carbon- 
ate, dolomite a double carbonate of calcium and mag- 
nesium, serpentine a silicate of magnesium, and gyp- 
sum or calcium sulphate. All rocks and minerals are 
subject to disintegration and change in chemical com- 
position and physical properties. The process of soil 
formation has resulted in numerous chemical and 
physical changes. These changes are still taking place, 
and as a result plant food is constantly being made 
available. 



56 SOII.S AND FERTILIZERS 

Chemical Composition of Rocks^^ 

i ^' "^ I 

S^ |o tri i9. in ^^ t^ ^d 
coo: <i1<J P^tij cc!^; i-Jo SS Unfe ^K 

Quartz 95-100 

Feldspar 55-67 20-29 0-12 i-io i-ii 

Kaolin 46 39 14 

Apatite 53 (Pjjs) 

Mica 40-45 12-37 5-12 1-5 

Hornblende... 40-55 0-15 

Granite 60-80 10-15 4-5 2-3 



67. Value of Geological Study of Soils. — Agri- 
cultural geology i.s a valuable aid in studying soil 
problems, but like other sciences it is incapable alone 
of solving all of the problems of soil fertility. 
Means have not as yet been devised for accurately de- 
termining the extent of rock disintegration and the 
rapidity with which it has taken place or the extent 
to which disintegrated minerals have been removed 
from rocks by leaching and other agencies. It is 
known that the rate of weathering of soils is influenced 
by various factors, as origin, texture, composition, 
humidity and other climatic conditions, presence of de- 
caying organic matter, micro-organisms, mechanical 
treatment and manipulation of the soil, fertilizers, 
sun light and vegetation. Some of these agencies for 
soil disintegration are under the control of the farmer 
and are utilized by him in rendering plant food avail- 
able. 



CHAPTER III 



THE CHEMICAL COMPOSITION OF SOILS 

68. Elements Present in Soils. — Physically consid- 
ered, a soil is composed of disintegrated rock mixed 
with animal and vegetable matter; chemically con- 
sidered, the rock particles are composed of a large 
number of simple and complex compounds, each com- 
pound in turn being composed of elements chemically 
united. Elements unite to form compounds, com- 
pounds to form minerals, minerals to form rocks, and 
disintegrated rocks form soil. When rocks decom- 
pose, the disintegration, except in a few cases, is never 
carried to the extent of liberating the elements, but 
the process ceases when the minerals have been broken 
up into compounds. While there are present in the 
crust of the earth between 65 and 70 elements, only 
about 15 are found in animal and plant bodies, and of 
these but 12 are absolutely essential. Only four of 
the elements which are of most importance are at all 
liable to be deficient in soils. These four elements 
are : nitrogen, phosphorus, potassium, and calcium. 

69. Classification of the Elements. — The elements 
found most abundantly in soils are divided into two 
classes : 



58 SOILS AND FERTILIZERS 

Acid-forming elements Base-forming elements 

Oxygen O Aluminum Al 

Silicon Si Potassium K 

Phosphorus P Sodium Na 

Sulphur S Calcium Ca 

Chlorine CI Magnesium Mg 

Nitrogen N Iron. Fe 

Hydrogen H 

Carbon C 

Boron, fluorine, manganese, and barium are usually 
present in small amounts, besides others which may 
be present in traces, as the rare elements lithium and 
titanium. 

For crop purposes the elements of the soil may be 
divided into three classes. 

1. Essential elements most liable to be deficient : 
nitrogen, potassium, phosphorus, and calcium. 

2. Essential elements usually abundant : iron, mag- 
nesium, and sulphur. 

3. Unnecessary and accidental elements, usually 
abundant, as chlorine, silicon, aluminum, and man- 
ganese. 

70. Combination of Elements. — In dealing with 
the composition of soils, the percentage amounts of 
the individual elements are not given, except in the 
case of nitrogen, but instead, the percentage amounts 
of the various oxides. This is because the elements 
do not exist as free elements in the soil, but are com_ 
bined with oxygen and other elements to form com. 
pounds. When considered as oxides, the acid- and base- 
o rming elements may form various compounds as : 



Calcium 



SILICON 59 



rSilicate 
Phosphate 
Chloride 
Sulphate 
Carbonate 



Potassium.. 

Sodium 

Magnesium 
Iron 




The following reactions will explain some of the 
more elementary forms of combinations : 

CaO + SiO, = CaSiO, CaO + N2O5 ^ Ca(N03)2 

sCaO + P^Og =Ca3(PO,)2 K.O + SO3 = K2SO4 

CaO + SO3 = CaSO, Na20 + SO3 ^ NaaSO, 

CaO + CO2 = CaCOs MgO + SO3 = MgSO^ 

When considered as the oxide, calcium may com- 
bine with any of the oxides of the acid-forming ele- 
ments, as indicated by the reactions, to form salts. 
Bach of the compounds formed from the more com- 
mon elements may have a separate value as plant 
food, hence it is important to consider the combina- 
tions of each element separately. 

ACID-FORMING ELEMENTS 

71. Silicon. — The element silicon makes up from 
a quarter to a third of the solid crust of the earth and 
next to oxygen is the most abundant element found 
in the soil. Silicon never occurs in the soil in the 
free state. It either combines with oxygen to form 
silica (SiO^), or with oxygen and some base-forming 
element or elements to form silicates. Silica and the 
various silicates are by far the most abundant com- 
pounds present in the soil. Silicon is not one of the 
elements absolutely necessary for plant growth, and 



6o SOILS AND FERTILIZERS 

even if it were, all soils are so abundantly supplied 
that it would not be necessary to use it in fertilizers. 

72. Double Silicates. — When two or more base- 
forming elements are united with the silicate radical, 
a double silicate is formed. In fact the double sili- 
cates are the most common forms present in soils. 
There are also a number of forms of silicic acid which 
greatly increase the number of silicates, and a study 
of the composition of soils is largely a study of these 
various silicates. 

73. Carbon is an acid-forming element and belongs 
to the same family as silicon. It is found in the soil 
as one of the main constituents of the volatile or 
organic compoimds. Carbon also unites with oxygen 
and the base-forming elements, producing carbonates, 
as calcium carbonate or limestone. The carbon of the 
soil takes no direct part in forming the carbon com- 
pounds of the plant. It is not necessary to apply 
carbon fertilizers to produce the carbon compounds of 
plants because the carbon dioxide of the air is the 
source for crop production. It is estimated that there 
are 30 tons of carbon dioxide in the air over every 
acre of the earth's surface. ^^ The carbon in the soil 
is an indirect element of fertility, because it is usually 
combined with elements, as nitrogen and phosphorus, 
which are absolutely necessary for crop growth. 

74. Sulphur occurs in all soils mainly in the form 
of sulphates, as calcium sulphate, magnesium sul- 
phate and sodium sulphate. It is an important ele- 
ment of plant food. There is generally less than 



NITROGEN 6 1 

o.io per cent, of sulphuric anhydride in ordinary 
soils, but the amount required by crops is small and 
there is usually an abundance in all soils. 

75. Chlorine is present in all soils, generally in 
combination with sodium, as sodium chloride. It may 
be in combination with other bases. Soils which con- 
tain more than o.io per cent, are, as a rule, sterile. 
Chlorine is present in the soil in soluble forms. It 
occurs in all plants, although it is not absolutely 
necessary for plant growth, and its combination in 
fertilizers is unnecessary. Chlorine with sodium, as 
common salt, is sometimes used as an indirect 
fertilizer. 

76. Phosphorus, one of the essential elements for 
plant growth, is combined with both the volatile and 
non-volatile elements of the soil. Plants cannot make 
use of it in other forms than those of phosphates. 
Phosphorus is usually present in the soil as calcium 
phosphate, magnesium phosphate, or aluminum phos- 
phate, and may also be combined with the humus, 
forming humic phosphates. The form in which the 
phosphates are present, as available or unavailable, is 
an important factor in soil fertility. Soils are quite 
liable to be deficient in phosphates, inasmuch as they 
are so largely drawn upon by many crops, particularly 
grain crops where the phosphates accumulate in the 
seed,* and are sold from the farm. 

77. Nitrogen. — This element is present in soils in 
various forms. As a mineral constituent it is com- 
bined with oxygen and the base-forming elements as 



62 SOII.S AND FERTILIZERS 

potassium, sodium, or calcium, forming nitrates and 
nitrites, which, on account of their sohibility, are 
never found in average soils in large amounts. Nitro- 
gen is present mainly in organic combinations, being 
associated with carbon, hydrogen, and oxygen as one 
of the elements forming the organic matter of soils. 
Nitrogen may also be present in small amounts in the 
form of ammonia, or of ammonium salts, derived from 
rain water and from the decay of vegetable and ani- 
mal matter. While nitrogen is present in the air in 
a free state in large amounts, it can be appropriated 
indirectly as food in this form by only a limited num- 
ber of plants. For ordinary agricultural crops, par- 
ticularly the cereals, nitrogen must be supplied 
through the soil as combined nitrogen. This element 
is the most expensive and is liable to be the most de- 
ficient of any of the elements of plant food. .No other 
element takes such an important part in agriculture or 
in life processes. 

78, Oxygen. — Oxygen is combined with both the 
acid- and base-forming elements and is present in 
nearly all of the compounds of the soil. It has been 
estimated that about one-half of the crust of the earth 
is composed of oxygen, which is found in large 
amounts combined with silicon, forming silica. That 
which is held in chemical combination in the soil 
takes no part in the formation of plant tissue. In ad- 
dition to being present in the soil, oxygen constitutes 
eight-ninths of the. weight of water and about one-fifth 
of the weight of air. It also forms about 50 per cent. 



ALUMINUM 63 

of the compounds found in plants and animals. Oxy- 
gen in the interstices of the soil is an active agent in 
bringing about many chemical changes, as oxidation 
of the organic matter, and disintegration of the soil 
particles. 

79. Hydrogen. — This element is never found in a 
free state in the soil, but is combined with carbon and 
oxygen as in animal and vegetable matter, with oxy- 
gen to form water, and in a few cases with some of 
the base elements to form hydroxides. It is not found 
in large amounts in the soil, and that which forms a 
part of the tissues of plants and animals comes from 
the hydrogen in water. Hydrogen in the organic 
matter of soils takes no part directly in producing the 
hydrogen compounds of plants. On account of its 
lightness, hydrogen never makes up a very large pro- 
portion, by weight, of the composition of bodies. 

BASE-FORMING ELEMENTS 

80. Aluminum is present in the soil in the largest 
quantity of any of the base elements. It is calculated 
that it forms from 6 to 10 per cent, of the solid crust 
of the earth. As previously stated aluminum is one 
of the constituents of clay, and is not necessary for 
plant growth. Physically, however, the aluminum 
compounds take an important part in soil fertility. 
Aluminum is usually in combination with silica or 
with silica and some base-forming element, as iron, 
potassium, or sodium. The various forms of alumi- 
num silicates are the most numerous compounds pres- 
ent in soils. 



64 SOILS AND FERTILIZERS 

8i. Potassium is present in the soil mainly in the 
form of silicates, and is one of the elements absolutely 
necessary for plant growth. The term potash (potas- 
sium oxide, K^O) is usually employed when the potas- 
sium compounds are referred to. The amount and 
form of the soil potash have an important bearing 
upon fertility. Potassium is one of the three elements 
of plant food usually supplied in fertilizers. The 
form in which it is present in the soil and its 
economic supply as plant food, are important factors 
of crop growth, and are considered in detail in Chap- 
ter VIII. The amount of potash in soils ranges 
from 0.02 to 0.8 per cent. In a fertile soil it rarely 
falls below 0.2 per cent. 

82. Calcium is present in the soil in a variety of 
forms, as calcium carbonate, calcium silicate, and 
calcium phosphate. The calcium oxide (CaO) of 
the soil is generally spoken of as the lime content. 
Calcium carbonate and sulphate are important factors 
in imparting fertility. A subsoil with a- good supply 
of lime will stand heavy cropping and remain in ex- 
cellent chemical and physical condition for crop 
growth. In a good soil there is usually 0.2 per cent, 
or more of lime mainly as calcium carbonate. 

83. Magnesium is present in all soils and is usually 
associated with calcium, forming the mineral dolo- 
mite, which is a double carbonate of calcium and 
magnesium. Magnesium may also be present in the 
soil in the form of magnesium sulphate or magnesium 
chloride. All crops require a certain amount of mag- 



ACID-SOLUBIvB MATTER OF SOII.S 65 

nesia in some form, in order to reach maturity and 
produce fertile seeds. There is generally in all soils 
an amount sufficient for crop purposes, hence it is not 
necessary to consider this element in connection with 
fertilizers. 

84. Sodium is found in the soil mainly as sodium 
silicate, and is present to about the same extent as 
potassium which it resembles chemically in many 
ways. It cannot, however, replace in plant growth 
the element potassium. Inasmuch as sodium takes 
an indifferent part in plant nutrition it is never used 
as a fertilizer except in an indirect way. 

85. Iron is an element necessary for plant food and 
is found in all soils to the extent of from i to 4 per 
cent. Crops require only a small amount of iron, 
hence there is always sufficient for crop purposes. 
Iron is present in soils in the form of oxides, hydrox- 
ides, and silicates. 

FORMS OF PLANT FOOD 

86. Three Classes of Compounds. — For agricul- 
tural purposes, the compounds present in soils may be 
divided into three classes i^^ (i) Compounds soluble 
in water and dilute organic and mineral acids ; (3) 
compounds soluble in more concentrated acids ; (3) in- 
soluble compounds decomposed by strongest acids and 
fluxes. 

87% Water- and Dilute Acid-soluble Matter of Soils. 
— This class includes silicates and other compounds of 
potash, soda, lime, magnesia, phosphorus, etc., which 
are soluble in the soil water and in very dilute organic 

(5) 



66 SOILS AND FERTILIZERS 

and mineral acids, and represents the most soluble and 
the most active and valuable forms of plant food. 
There is only a very small amount in these forms. 
In lOO pounds of soil, rarely more than 0.005 pound 
of any one of the important elements is soluble in 
the soil- water or more than 0.05 pound in dilute or- 
ganic acids. 

Experiments have shown that the soluble plant 
food from a fertile soil is not sufficient for plant 
growth. ^5 When oats, wheat and barley were seeded 
in prepared sand and watered with the leach- 
ings from a pot of fertile soil, they made only a lim- 
ited growth. For comparisons with plants grown in 
fertile soil, see Plate I. The oats grown in the pre- 
pared sand and watered with soil leachings assimilated 
only 25 per cent, as much phosphoric acid as the 
plants grown in fertile soil. 

88. Acid Soluble Matter of Soils,— The plant food 
of the second class is in a somewhat more insoluble 
form, and consists of all those compounds and zeolitic 
silicates which are soluble in hydrochloric acid of 
23 per cent, strength, sp. gr. 1.115. This represents 
the limit of the solvent action of the roots of plants. ^^ 
In this second class are also included all of the mineral 
elements combined with the humus and soluble in 
dilute alkalies. As a rule, not over 15 or 20 per cent, 
of the total soil is in forms soluble in hydrochloric 
acid, and of the more important elements only i to 6 
per cent, form a part of this 1 5. In 200 samples of soil, 
the potash, nitrogen, lime, magnesia, and phosphoric 
and sulphuric acids, amounted to 3.5 per cent. In 




I 


.1 ■^"'- . W'*^ vj 






1 r^' 1^/ .r> li"'^- 




■■^\>^-^,% 


. V- 1^ Hi !/ 




■ ' i\. ■■:■■■ -'.^ -/^. i 


/ , \ :S^ 


\ 




■ ^^' -.•■,«p--'--*_, ; 




m^^^^f^ 


"JaL. t...v^ 




^^H^' 


l^^^^^^^Umi ^;?pi;»^^.,.-*., ^^ 




JHJ^' 




»-=-«-— 


*PP8s^WKP»w»aM^* , , » y 


Hi BARLEY ^^^ OATS ™ 


*™*^ 



Plate I. 



ACID-INSOLUBLE MATTER OF SOILS 



67 




Total /n^o/ut?/e/iatfer' 



Fig. 17. Graphic composition of 200 soils. 
I. Nitrogen. 2. Potash. 3. Phosphoric acid. 

many fertile soils the sum of the nitrogen, phosphoric 
acid, potash, lime, magnesia, and sulphuric and car- 
bonic anhydrides is less than 1.50 per cent. This 
means that in every 100 pounds of soil there are only 
from ic5 to 3.5 pounds of matter which can take any 
active part in the support of a crop, and 96 to 98.5 
pounds are present simply as so much inert material. 
Not all of the plant food soluble in hydrochloric acid 
is equally valuable. In fact, the acid represents more 
than the limit of the crop's feeding power, when there 
is not enough of more soluble forms to aid in the first 
stages of growth. 

89. Acid-Insoluble Matter of Soils. — This class in- 
cludes all of those compounds of tlie soil which re- 
quire the joint action of the highest heat and the 
strongest chemicals in order to decompose them. The 



68 SOILS AND FERTILIZERS 

insoluble residue obtained after digesting a soil with 

Strong hydrochloric acid, contains potash, soda, and 

limited amounts of magnesia, 

and phosphoric acid, with 

other elements which are of 

no value as plant food. 

When seed was planted in 

soil extracted with strong 

hydrochloric acid, it made 

no growth after the reserve 

food in the seed had been 

exhausted. A plant grown 

in such a soil is shown in 

the illustration, '7 Fig. i 

The acid-insoluble matter 
of soils is capable of under- 
going disintegration and in 
time may be changed to the 
second or zeolitic class of 
silicates. This process, how- 
ever, is too slow to be relied 
upon as an immediate source 
of plant food. 

In the following table the 
percentage amounts of con.- 't^^.^f-XZ!" 
pounds soluble and insoluble chloric acid, 

in hydrochloric acid are given :'7 




SOI^UBLK AND INSOLUBLE POTASH, KTC. 69 

wheat Heavy clay Grass and 
soil. soil. grain soil. 
Solu- Insolu- Solu- Insolu- Solu- Insolu- 
ble in ble ble in ble ble in ble 
HCl residue HCl residue HCl residue 

Insoluble matter... 63.07 84.77 84.08 

Potash 0.54 2.18 0.21 3.46 0.30 1.45 

Soda 0.45 3.55 0.22 2.95 0.25 0.25 

Lime 2,44 0.36 0.48 0.16 0.51 0.35 

Magnesia 1.85 0.25 0.34 0.47 0.26 0.46 

Iron 4.18 0.78 3.76 0.72 2.56 1.07 

Alumina 7.89 5,54 6.26 5.44 2.99 9.72 

Phosphoric acid..., 0.38 0.12 0,08 0.23 0.05 

Sulphuric acid o.ii 0.24 0.09 0.25 0.08 0.02 

The insoluble matter, after digestion with hydro- 
chloric acid, was submitted to fusion analysis, and the 
figures given under insoluble residue represent the 
amounts of potash, soda, etc., insoluble in acids. In 
the clay soil, 94 per cent, of the total potash is in 
forms insoluble in hydrochloric acid. 

90. Soluble and Insoluble Potash and Phosphoric 
Acid. — From the preceding table it is to be observed 
that the larger portion of the potash in the soil is in- 
soluble in hydrochloric acid. A soil may contain 
from 2 to 3 per cent, of total potash, and 90 per cent, 
or more may be in such firm chemical combination 
with aluminum, silicon, and other elements, as to re- 
sist the solvent action of plant roots. The larger por- 
tion of the phosphoric acid of ~ the soil is soluble in 
hydrochloric acid. In some soils, however, from 20 
to 40 per cent, is present as the third class of com- 
pounds. When a soil is digested with hydrochloric 
acid* the insoluble residue is usually a fine, gray 
powder. Some clay soils retain their red color even 
after treatment with acids showing that the iron is in 



yo SOII.S AND FERTII.IZERS 

part in chemical combination with the more complex 
silicates. 

In order to decompose theinsolnble residue obtained 
from the treatment with h3^drochloric acid, fluxes, as 
sodium carbonate and calcium carbonate, are employed 
which act upon the complex silicates at a high tem- 
perature, and produce silicates soluble in acids. Plants, 
however, are unable to obtain food in such complex 
forms of chemical combination. 

91. Action of Organic Acids upon Soils. — Dilute 
organic acids, as a i per cent, solution of citric acid, 
have been proposed as solvents for the determination 
of easily available plant food. It has been shown in 
the case of the Rothamsted soils which have produced 
50 crops of grain without manures, and which are 
markedly deficient in available phosphoric acid, that 
a I per cent, solution of citric acid dissolved only 0.003 
per cent, of phosphoric acid while the soil contained a 
total of 0.12 per cent. In the case of an adjoining 
plot which had received phosphate manures until the 
sell contained a sufficient amount of available phos- 
phoric acid to produce good crops, there was present 
0.03 per cent, of phosphoric acid soluble in ^ i per 
cent, citric acid solution. ^3 

Dilute organic acids are, to a certain extent, capable 
of showing deficiency of plant food. A soil which 
shows 0.03 per cent, of potash or phosphoric acid sol- 
uble in I per cent, citric acid is, as a rule, well stocked 
with available phosphoric acid. Prairie soils of high 
fertility yield from 0.03 to 0.05 per cent, of both pot- 



ACTION OF ORGANIC ACIDS UPON SOILS 7 1 

ash and phosphoric acid soluble in dilute organic 
acids ; soils which are deficient in these elements usu- 
ally contain less than o.oi per cent. 

The action of a single organic acid of specific 
strength cannot be taken as the measure of fertility 
for all soils and crops alike, because different plants 
do not have the same amount or kind of organic acid 
in the sap. Of the various organic acids, citric pos- 
sesses the greatest solvent action upon lime, magnesia, 
and phosphoric acid, while oxalic has the strong- 
est solvent action upon the silicates. Tartaric acid 
appears to be less active as a solvent than either citric 
or oxalic acid. The combined use of dilute organic 
acids, as citric, with hydrochloric acid (sp. gr. 1.115), 
will generally give an accurate idea of the character 
of a soil. A fifth-normal solution of hydrochloric acid 
has also been proposed as a measure of the soil's active 
phosphoric acid, and has given satisfactory results.^^ 

The use of dilute organic acids renders it possible 
to detect small amounts of readily soluble phosphoric 
acid and potash. It has been stated that when a soil 
has been manured a few years with a phosphate fer- 
tilizer and brought into good condition as to avail- 
able phosphoric acid, a chemical analysis will fail to 
detect any difference in the soil before or after the 
treatment with fertilizer. In the case of hydrochloric 
acid as a solvent, this is true because an acre of soil 
to the depth of one foot weighs about 3,500,000 lbs. 
and 500 pounds of phosphoric acid would increase the 
total amount of phosphoric acid about 0.015 per cent. 
When a dilute organic acid is used, only the more 



72 



SOILS AND FERTILIZERS 



easily soluble phosphoric acid is dissolved, and this 
readily allows fertilized and unfertilized soils to be 
distinguished. By the use of dilute organic acids and 
salts decided differences have been shown between soils 
fertilized and unfertilized with potash. ^^ 

92. Sampling of Soils. — A composite sample of 
soil is obtained from a field by taking several small 
samples to a depth of 6 to 9 inches, from different 
places, and uniting them to form one sample. Samples 
of subsoil also are taken from the same places. There 
is usually a sharp line of demarkation between the 
surface and subsoils. It is the aim to secure in both 
cases as representative samples as possible. All 
coarse stones and roots are removed and a record is 
made of the amount of these materials. The soil is 
air-dried, the hard lumps are crushed, and the mate- 
rials mixed and passed through a sieve 
with holes 0.5 mm. in diameter. Only 
the fine earth is used for the chemical 
analysis. 

93. Analysis of Acid- soluble Ex- 
tract of Soils. — Ten grams of soil are 
weighed into a soil digestion flask, 
and 10 cc. hydrochloric acid (sp. gr. 
I.I 15), are added for every gram of soil 
used. The soil digestion flask is then 
placed in a hot water-bath and the 
digestion carried on for twelve hours 
at the temperature of boiling water.^^ 
After digestion is completed the con- 
tents of the flask are transferred to a filter and separated 




Fig. 19. Diges- 
tion flask. 



ACID-SOI.UBI.K EXTRACT OF SOII.S 



73 



2^ ^ !=^S 

^ ?S 2 -• ~ 



^ o 






•:« 02 !-( 



D p o a ;:< 



= 2-3 g 



0-' 



'-+»'^ en 
C O en C 



-T" cr t3 cfi (VQ D^ 

o o P^ o ^3 o 

S3 S' ::j 2 <T) tr 
*" ^ o a.p,o 

en 2 3 •=« 



TS O 






ST — "-t Li 

(T) n "^ ^* 

. ^ — ^. CL 



Sr'P 



5-'2. 

O rK 

P3 ^. 



p en 

" 5 



o fc B "TJ CI. 



fi 



2 B^. S O 
^ B ^ 



P-- 3* 15. 



Ca B P S- 

ti 3. "-f p 

a /^ <^ 

-» "r fD B' 



CL w g^O-n, 



"-^ rD o 
0) HI a, 
l-t I Pi 



'T3 O 



-n 



(T) 



O 

p, 

.-11 

en I 
C 



b' C/5 

rt o 

* S" 

y (T) 

3 en 

7 rt 

3- CL 



3^ 3- 

^ 3 
rt n 



en 
rt 



en 



O 

I ^ 

rt Pj 

^ 3. 



74 SOII.S AND FEKTII.IZERS 

into an insoluble part, and the acid solution which 
contains the soluble compounds of the various elements. 
The table on page ']'^ gives a general idea of the 
process of soil analysis. One-half of the acid solu- 
tion is used for obtaining the metals as noted 
on page ^2i' '^^^ second half is divided into two 
portions. The first portion is used for the deter- 
mination of phosphoric acid, which is precipitated 
with ammonium molybdate. The second portion is 
used for the determination of sulphuric acid, which is 
precipitated as barium sulphate. Carbon dioxide 
is determined in a fresh portion of the original soil • 
the acid is liberated with hydrochloric acid and the 
carbon dioxide retained by absorbents and weighed. 
The nitrogen and humus are determined in separate 
portions of the original soil. The analysis of soils 
involves the use of accurate and well-known methods 
of analytical chemistry, a discussion of which would 
not be germane to this work. 

94. Value of Soil Analysis. — Opinions differ as to 
the value of soil analysis. It is claimed by some that 
a chemical analysis of a soil is of no practical value 
because it fails to give the amount of available plant 
food. A soil may have, for example, 0.4 per cent, of 
potash soluble in hydrochloric acid and still not con- 
tain sufhcient available potash to produce a good crop, 
while another soil may contain 0.2 per cent, of potash 
soluble in hydrochloric acid and produce good crops. 
While these facts are frequently true, it does not 
necessarily follow that the chemical analysis of a soil 



VALUE OF SILT ANALYSIS 75 

is of no value. Other solvents than hydrochloric acid 
are used in soil analysis with excellent results. Hydro- 
chloric acid is generally used because it represents the 
limit of the solvent power of plants. ^^^ 'Xhe figures 
obtained by the use of hydrochloric acid are valuable 
inasmuch as they indicate whenever an element is 
present in amounts which are too limited to admit of 
crop production. Suppose a soil contain 0.02 per cent, 
of acid-soluble potash ; this would be too small an 
amount to produce good crops. On the other hand, 
the soil might contain 0.5 per cent, and yet not have 
sufficient available potash for crop growth. Hence 
it is, that in interpreting results, the hydrochloric acid 
solvent may show when a soil is wholly deficient in 
any one element, as is sometimes the case, but it does 
not necessarily show a deficiency in the case of a soil 
rich in acid-soluble potash; this can, however, be ap- 
proximately indicated, by the use of other solvents, as 
explained in Section 91. Hydrochloric acid is mainly 
valuable in determining the general character of the 
soil, rather than its amount of available plant food. 

In the analysis of soils their reaction as acid, alka- 
line, or neutral, should be determined, because plant 
food exists in a different form in each class of soils. 
If a soil contain from 0.3 to 0.5 per cent, or more of 
lime and from o.i to 0.4 per cent, of combined carbon 
dioxide, and is not strongly alkaline, there is a reason- 
able content of lime carbonate. If, however, the soil 
contain only a trace of carbon dioxide, the lime is 
not present as carbonate, but is probably present as a 



76 SOIIvS AND FKRTII.IZERS 

silicate, in which case the soil may be deficient in ac- 
tive lime compounds. 

In the case of phosphoric acid, a soil which gives 
an alkaline or neutral reaction, contains 0.15 per 
cent, of phosphorus pentoxide and is well supplied with 
organic matter and lime, is amply provided with phos- 
phoric acid, and under such conditions the extensive 
use of phosphate fertilizers is not required, except pos- 
sibly for special crops. Hilgard states that should 
the per cent, of phosphoric acid be as low as 0.05, 
there is, in all probability, a poverty of this element. 
It frequently happens that in acid soils the phosphoric 
acid is unavailable until a lime fertilizer is used to 
neutralize the acid. 

Soils containing less than 0.07 per cent, of total 
nitrogen are usually deficient. A soil containing as 
high as 0.15 or 0.2 per cent, of nitrogen may fail to re- 
spond to crop production. Such cases are generally 
due to some abnormal condition of the soil, as a lack 
of alkaline compounds which are necessar}^ for nitri- 
fication. The appearance of the crop is the best indi- 
cation as to a deficiency of nitrogen. 

A soil which contains less than o.io per cent, of pot- 
ash soluble in hydrochloric acid is quite apt to be de- 
ficient in this element. Soils which contain 0.5 per 
cent, or more of lime carbonate will produce good 
crops on a smaller working supply of potash than soils 
which are proverty-stricken in lime. As a rule the 
best agricultural soils contain from 0.3 to 0.6 per cent. 
of potash. Sandy soils of good depth may contain 



VAI.UE OF SILT ANALYSIS 77 

less plant food than the figures given, and not be in 
need of fertilizers. 

The term volatile matter is sometimes confused with 
the term organic matter. The volatile matter includes 
the organic matter and the water which is held in 
chemical combination as in the hydrated silicates. A 
soil may have a high per cent, of volatile matter and 
contain very little organic matter. Indeed all clays 
contain from 5 to 9 per cent, of water of hydration. 
The per cent, of humus, as will be explained in the 
next chapter, does not represent all of the organic 
matter. 

The best results are obtained from soil analyses 
when an extended study is made of the soils of a lo- 
cality. Then an unknown soil of that locality can be 
compared with a productive soil of known composition. 
An isolated soil analysis, like an isolated analysis of 
well water, frequently fails in its object because of a 
lack of proper normal standards for comparison. 
When extended series of soil analyses have been 
made, much valuable information has been obtained. 

Suppose a soil -contain 0.40 per cent, of acid-soluble 
potash and field experiments indicate that there is a 
deficiency of available potash. This may be due to 
some abnormal condition of the soil, as an insufficient 
amount of other alkaline compounds as calcium car- 
bonate to take the place of the potash which has been 
withdrawn by the crop, in which case the deficiency 
of potash can be remedied without purchasing solu- 
ble potash fertilizer, to become insoluble by fixation 
processes. If a soil contain only 0.04 per cent, of 



78 - SOILS AND FERTILIZERS 

acid-soluble potash, the purchasing of potash fer- 
tilizers is more necessary, but with 0.40 per cent, 
of acid-soluble potash the way is open to render this 
potash available for crops. The various ways of ren- 
dering acid-insoluble potash and other compounds 
available for crop production, as by rotation of crops, 
use of farm manures, use of lime and green manures, 
or by different methods of cultivation have not been 
sufficiently studied as yet to offer a solution to all of 
the problems of how to render inert plant food avail- 
able. 

95. Distribution of Plant Food. — In studying the 
chemical composition of a soil, the surface soil and 
the subsoil both require consideration. It frequently 
happens that the surface soil and subsoil have entirely 
different chemical, as well as physical, properties, and 
that a soil fault, as lack of potash in the surface soil, is 
corrected by a high per cent, of that element in the 
subsoil. This is particularly true of the western prairie 
soils, where the surface soils generally contain less 
potash and lime, but more nitrogen and phosphoric 
acid than the subsoils. When jointly considered the 
surface and subsoil have strong crop-producing powers, 
but if considered separately each would have weak 
points. 

Since crops take their food mainly from the silt and 
clay, the amount of plant food present in these grades 
of particles determines largely the reserve fertility of 
the soil. A soil in which 70 per cent, of the total 
potash is present in the silt and clay, is in better con- 
dition for crop production than a similar soil with a 



COMPOSITION OF TYPICAIv SOILS 79 

like amount of potash which is present mainly in the 
sand. Because a soil has a given composition, it does 
not follow that all of the different grades of particles 
have the same composition. In fact the different 
grades of soil particles in one soil may have as varied 
a composition as is met with among different soils.^^ 

The figures under i in the table give the composi- 
tion of the particles, while under 2 are given the re- 
sults calculated on the basis of the total amount of 
each element. For example, the clay contains 1.47 
per cent, of potash, while 50.8 per cent, of the total 
potash of the soil is in the clay particles. 

A soil may contain a comparatively low per cent, of 
potash or phosphoric acid, mainly in the finer particles 
and evenly distributed so that the crop is better sup- 
plied with food than if more were present in the 
larger particles, unevenly distributed. The distribu- 
tion of the plant food in the soil has not been so ex- 
tensively studied as the question of total plant food. 
The distribution of plant food in both surface soil and 
subsoil, as well as in the various grades of soil parti- 
cles, is an important factor of fertility. 

96. Composition of Typical Soils.— A few exam- 
ples are given, in tabular form, of the chemical com- 
position of soils from different regions in the United 
States. On account of variations in the same locality, 
the figures represent the composition of only limited 
areas of soils. There have been made in the United 
States a large number of soil analyses, which as yet 
have not been compiled nor studied in a systematic 
way. 



8o 



SOILS AND FERTILIZERS 



1^ 


''^f ^ o o 


8 


^ 


M 


^ S^ 2^ 


?. 




g- 


CO vO ON 00 


^ 


8 


d 


►-* 00 oo' 6 


d 


ON 



.2 S 



C ID 



tg c M 



S.?^ 



O O O O ''t -* o 



CO vO *0 Tj- 



(NOOOOf^<NOO 



CO C^ <N CN 



^ as o ^ 

(S O l-H ^ 

6 d d 



O N o 

d 



CN CO N 

o o\ 

6 6 



CO fO C3^ r^ lO 

ti 00 ^ O <N '^ 



w w <i^ rt • ^■ 

O Ph S N c o 

a.'" o 00 

5 



^ 
s 


1 


o 


rt 


C 
t—t 


£ 



o d 



C/2 i-T 



M ON w 

■-^^ O W 

lo oo' d 



^^< 



O CO 



13 

"o 'S ii 

3^ "^ R 
'Con 

<^ ^ '-M 

PM 02 > 



COMPOSITION OF TYPICAL SOILS 



8l 



% ffi 




p: 


3 


B 


^ 


c 

tn 



O 05 



? ^ ^ ^ ^. ^ 

t g S ^ 



^ p^ g- a 



o ti: 



ft! 



Da 



^ ^ n O 

'^ rn f\i ^ 

\ 3 



O Cn 


P 


00 


^^ 


D 


8§ 


o o 


CK! 


V 


:: .g^ 




v3 


Cn 




% 


00 to 
o 




^1 



en (0 p p •<» 4^ M K) p p c^ -^J Surface. 
in h~ *mU) com bo4i4^cn-P»- ON Per cent, 

tn to M OOVO OOCn.4^Cn^OJ4^ 

MM Ji' 

i^ -f^ P P P V^ f" V P .O P° ."^ Subsoil. 

M Jo M *M ^ ^ i. 4^ 4^ to d> fo Per cent, 

to ONO^ lo COOOCn COCn^ m 



O O O On 10 Surface. 
4^ ^ Li I to 6 in, 
c/i ^j O Per cent. 



OOOOOJtOOv_/.^v^w. — 

(o in b CO M vb Ck. a^ lo 4^ -^ Ck> I to 6 inches. 

oca a^C/1VDC^> OOvD 0^'^^ "~ 



vp P p p f' C>> p ., _ __ _. - 

*mc>) c to avodjCj^i.ji^Oivi) 

to ON4i>. a\CN)^-n ONO (O O — "■ 



V! fD 



f":* Subsoil. 

6 to 12 inches. 
oo oi Per cent. 



^ 



coiooptot/ipojoo 

to 4i- b *M vb -^r vb to d> bs 4^^ vb -p^-^^^f 
»<tc/icn^j Mvo M i-i M.p^ 00^ ^^~ cent. 



;^ Subsoil. 

30 to 36 inches. 



M p p p M _M p p p p , 4^ Surface. 
cnOMMtototo4^K)M. ON Per cent 
M4^0C.^>^M4^^^Ja^.O^ ''^^ ^'^^'" 



p p p p M M p p p p . c^ Subsoil. 
•<j b b b 6\ to M oj io "m \ in Percent, 
4i'4^C/iv.04^MvOC/i^-JCn» 00 



w 3 



1^ 

J - 



< S 



^ 



OOOOOCntoOOOO 



•<» p p p "^t f>. p p p p 

O O b M OJ M >-. to M d> 

to ONOJ M^CnvOOJOJCa 



to O O O O 



^MOOCntoOtooO 



MS Surface. 


u 

p 


vb Per cent. 


!^ 





7) •-'• 




•2.3 


^ Subsoil. 


^% 


Cj Per cent. 


l 


M 


n ^ 


O) <: 


3 rt 


^ Per cent. ? 




i^ Surface. c 


it< 


vb Percent. i 


:B» 



(6) 



82 



SOILS AND FERTILIZERS 



c o 



MfOVOMOOO-^CC 



<N xt- O O 



OOOOC^iOOOOOO 



t^ c^ o o o o 



vX) o o o o 



^- "^ VO vo 


rO O 








O VO CO 


M 


o 


'^ 


t^ o 



u . 

o 



Cfi 


lO 00 


-* 


CO 


CO 


CO 


CO 


rO 




; 


r^ 


o 




o 


o 


M 


o 


CO CO 









" 


CN 


O 


^ 




o 


CN 




00 


cs 


CO 


^ 


^ 


s; 


a 


^ 


-* 


" 


o 


lO 




CO 


!>. 


o 


o 


CO 


CN 


1 


^ 


^ 


'^ 


lO 


o 


^ 


-* 


04 

to 


o 


2 




^ 


5 




M 


o 


o 


o 


o 


o 


CN 


o 




'"' 


1 


vS 




^ 


- 


"S 


^ 


^ 


CO 


^ 


o 


: 


vg^ 



o o o o o 



,1- Cfl O! 



<u 



c« 
p O •'- 

PM 0} H^ 



5P =^ 






III 

Oh ^ O 

Ah c/} a 



C 
en OJ 

::! bjo 



IMPROVING AI.KALI SOILS 83 

97. Alkaline Soils. — When a soil contains enough 
alkaline salts as sodium sulphate, sodium or potas- 
sium carbonate or chloride, to be destructive to vege- 
tation, it is called an ' alkali ' soil. These soils are 
found in semi-arid regions, and wherever conditions 
have been such that the alkaline compounds have not 
been drained from the soil. Occasionally calcium 
chloride is the destructive material. Chlorine in any 
ordinary- combination is destructive to vegetation 
when present to the extent of more than i part per 
1000 parts of soil. Of the various alkaline com- 
pounds potassium carbonate is one of the most in- 
jurious. Sodium sulphate is a milder form of alkali. 
When evaporation takes place, the alkaline compounds 
are deposited as a coating on the surface of the soil. 
Many soils supposed to be strongly alkaline, because 
a white coating is formed on the surface, simply con- 
tain so much lime carbonate that a deposit is formed. 
Excellent soils have been passed over as ' alkali' soils 
when in reality they are limestone soils. 

98. Improving Alkali Soils, ^^ — when a large tract 
of alkali is to be brought under cultivation the amount 
and kind of prevailing alkaline compound should be de- 
termined by chemical analysis. It frequently happens 
that drainage followed by deep and thorough cultiva. 
tion is all the treatment necessary. If the prevailing 
alkali is sodium carbonate a dressing of land plaster 
may* be applied so as to change the alkali from sodium 
carbonate to sodium sulphate, a less destructive form, 
the reaction being 

Na CO -f CaSO = CaCO + Na SO . 

23 4 3*24 



84 SOILS AND FERTILIZERS 

Some shrubs, as grease wood, and weeds, as Russian 
thistle, take from the soil large amounts of alkaline 
matter, and it is sometimes advisable to remove a 
number of such crops so as to reduce the alkali. A 
slightly beneficial effect is sometimes noticed on small 
' alkali ' spots where straw is burned and the ashes are 
used, forming potassium silicate. As a rule ashes are 
more injurious than beneficial, on an 'alkali' soil. 
Irrigation and thorough drainage, if continued long 
enough, will effect a permanent cure. Irrigation 
without drainage may cause a more alkaline condition 
by bringing to the surface subsoil alkali. The waters 
from some streams and wells are unsuited for irriga- 
tion on account of containing too much alkaline mat- 
ter. Mildly alkaline soils will usually repay in crop 
production all the labor which is expended in making 
them productive, and when brought under cultivation 
are frequently very fertile soils. A small amount of 
alkaline compounds in a soil is beneficial ; in fact, 
many soils would be more productive if they contained 
more alkaline matter. 

99. Improving Small Tracts of * Alkali ' Land. — 
When the places are located so that they can be under- 
drained at comparatively little expense, this should be 
done, as it will prove the best and most permanent 
way of removing the alkali. Good surface drainage 
should also be provided. Quite frequently a quarter 
or more of the total alkali in the soil will, in a dry 
time, be found near and on the surface. In such cases, 
and if the spots are small, a large amount of alkali 
can be removed by scraping the surface and then cart- 



ACID SOILS 85 

ing the scrapings away a.nd dumping them where they 
can do no damage. 

When preparing an ' alkali ' spot for a crop, deep 
plowing should be practiced, so as to open up the soil 
and remove the excess of alkaline matter from the 
surface. Where manure, particularly horse manure, 
can be obtained these spots should be manured very 
heavily. The horse manure, when it decomposes, fur- 
nishes acid products, which combine with the alkaline 
salts. The manure also prevents rapid surface evapora- 
tion. Oats are about the safest grain crop to seed on 
an ' alkali ' spot because the oat plant is capable of 
thriving in an alkaline soil where many other grain 
crops fail. 

'Alkali' soils are usually deficient in available 
nitrogen. The organism which carries on the work 
of changing the humus nitrogen to available forms 
cannot thrive in a strong alkaline solution. In many 
of these soils, as demonstrated in the laboratory, nitri- 
fication cannot take place. After thorough drainage and 
preparation for a crop, a few loads of good soil from a 
fertile field sprinkled on ' alkali ' spots will do much to 
encourage nitrification, by introducing the nitrifying 
organisms. 

100. Acid Soils. — When a soil is deficient in active 
alkaline matter, humic acids are formed from the 
decay of animal and vegetable substances. Acid soils 
are readily detected by the reaction which they give 
with sensitive litmus paper. In making the test the 
moistened soil is pressed against the blue litmus 
paper which changes to red in the presence of free 



86 SOII.S AND FERTILIZERS 

acids. Acid soils are made productive by using lime 
and other alkaline matter to neutralize the humic 
acid before applying farm and other manures. Acid, 
soils are not suitable for the production of clover and 
legumes. 

THE ORGANIC COMPOUNDS OF SOILS 

1 01 Sources of the Organic Compounds of Soils. — 

The organic compounds of soils are composed of the 
elements carbon, hydrogen, oxygen, and nitrogen. 
When vegetable and animal matter undergo decay in 
contact with the soil, compounds as carbon dioxide, 
water, ammonia,^^ organic acids, and various derivatives 
are formed, while some of the organic acids unite with 
the mineral matter of the soil to form humates. 
Micro-organisms take an important part in the decay 
of animal and vegetable matter and the production of 
organic compounds in soils. In some soils, the or- 
ganic compounds of plants, as cellulose, proteids, and 
carbohydrates like pentosans, are present, while in 
other soils these compounds have undergone partial 
oxidation. Some authorities claim (see Section 137) 
that a portion of the initial organic matter of soils is 
the result of the workings of carbon assimilating 
nitro-organisms. The main source of the soil's or- 
ganic matter, however, is the accumulated animal and 
vegetable remains which exist in various stages of 
decay. The organic matter of soils is a mechanical 
mixture of a large number of organic compounds, 
many of which have not as yet been studied. 

102. Classification of the Organic Compounds. — 
Various attempts have been made to classify the or- 



HUMIFICATlOfq- AND HUMATKS 87 

ganic compounds of the soil, but those which have 
been described are without doubt mixtures of various 
bodies, and not distinct compounds. An old classifi- 
cation by Miilder^9 ^vas humic, ulmic, crenic, and ap- 
procrenic acids. This classification does not include 
any nitrogenous matter containing more than 4 per 
cent, nitrogen, while organic matter with 8 to 10 per 
cent, and in some cases 18 per cent, of nitrogen is 
quite frequently met with ; hence this classification is 
incomplete as it includes only a part of the organic 
compounds of the soil. For practical purposes the 
organic compounds of soils may be divided into three 
classes : (i) Those of low nitrogen content, i to 4 per 
cent, of nitrogen ; (2) medium nitrogen content, 5 to 
10 per cent.; (3) high nitrogen content, 11 to 20 per 
cent. 

103, Humus. — The term humus is employed to 
designate the most active parts of the organic com- 
pounds. Humus is the animal and vegetable matter 
of the soil in intermediate forms of decomposition. 
From different soils, it is extremely varied in compo- 
sition ; in one soil it may have been derived mainly 
from cellulose, while in another it may have been de- 
rived from a mixture of cellulose, proteid bodies, and 
other organic compounds. The term humus, unless 
qualified, is a very indefinite one. The humus as given 
in the analyses of soils is obtained by extracting the 
soil, with a dilute alkali as ammonium hydroxide, 
after treating the soil with a dilute acid to remove the 
lime which renders the humus insoluble. 

104. Humification and Humates. — When the ani- 



88 SOILS AND FBRTILIZKRS 

mal and vegetable matter incorporated with soils un- 
dergoes decomposition there is a union of some of the 
organic compounds with the base-forming elements of 
the soil. The decaying organic matter produces or- 
ganic products of an acid nature. The organic acids 
and the base-forming products unite to form humate^ 
or organic salts, which are neutral bodies. This 
process is humification.^7 

Humic acid -\- calcium carbonate = calcium humate + COg. 
Humic acid + potassium sulphate = potassium humate, etc. 

The fact that a union occurs between the organic 
matter and the soil has been demonstrated by mixing 
with soils known amounts of various organic mate- 
rials, as cow manure, green clover, meat scraps, and 
sawdust, and allowing humification to go on for a year 
or more. After humification has taken place, the 
humus extracted from the soil contains more potash, 
phosphoric acid, and other elements than were present 
in the humus of the original soil and humus-forming 
material, showing that a chemical union has taken 
place between the decaying organic matter and the soil. 
The power of various organic substances to produce 
humates is illustrated in the following table. ^9- 85 

Humic phos- Humic 

_ , phoric acid. potash. 

Cow manure humus : Grams. Grams. 

In original manure and soil 1.17 1.06 

In final humus product (after hu- 
mification) 1.62 1.27 

Gain in humic forms 0.45 0.21 

Green clover huniiis : 

In original soil and clover 3.21 5.26 

In final humus product 3.74 4.93 

Gain in humic forms 0.53 (Loss) 0.33 



VALUE AND COMPOSITION OF HUMATES 89 

Humic phos- Humic 

phoric aeid. potash. 

Meat scrap hufnus : Grams. Grams. 

In original meat scraps and soil- • . 1.07 0.25 

In final humus product 1.18 0.36 

Gain o.ii o.ii 

Sawdust humus : 

In original sawdust and soil 0.85 0.67 

In final humus product 0.78 0.70 

Oat straw humus : 

In original straw and soil . 1.02 2.42 

In final humus product 1.03 2.41 

105. Comparative Value and Composition of Hu- 
mates. — The humus produced from nitrogenous 
bodies as meat scraps, is more valuable than that pro- 
duced from cellulose bodies, as sawdust, because the 
former has greater power of combining with the 
phosphoric acid and potash of the soil. The non- 
nitrogenous compounds, as cellulose, starch, and sugar, 
undergo fermentation but seem to possess little, if any, 
power to form humates. There is also a great differ- 
ence in soils as to their humus-producing powers. 
Soils deficient in lime or alkaline compounds possess 
only a feeble power to produce humates. There is 
also a marked variation in the composition of the 
humus produced from different kinds of organic matter. 
Straw, sawdust, and sugar, materials rich in cellulose 
and other carbo-hydrates, yield a humus characteris- 
tically rich in carbon and poor in nitrogen. Materials 
rich in nitrogen, like meat scraps, green clover, and 
manure, produce a more valuable humus, rich in nitro- 
gen and possessing the power to combine with the 



go SOII.S AND FERTILIZERS 

potash and phosphoric acid of the soil to form hu- 

mates. 

Composition oi^ Humus Produced by^*' 

Cow Green Meat Wheat Oat Saw- 
manure, clover, scraps, flour. straw. dust. Sugar^ 

Carbon 41.95 54.22 48.77 51.02 54.30 49.28 57.84 

Hydrogen 6.26 3.40 4.30 3.82 2.48 3.33 3.04 

Nitrogen 6.16 8.24 10.96 5.02 2.50 0.32 0.08 

Oxygen 45.63 34.14 35.97 40.14 40.72 47.07 39.04 

Total 100.00 100.00 100.00 100.00 100.00 lOD.oo 100.00 

Highest. I^owest. Difference. 

Carbon •• 57.84 41.95 15.89 

Hydrogen 6.26 2.48 3.78 

Nitrogen 10.96 0.08 10.88 

Oxygen 47.07 34.14 12.93 

Variations in composition are noticeable. The 
humus produced from each material as green clover, 
oat straw, or sawdust, is different from that produced 
from any other material. The humus from green 
clover is very complex in nature. It contains both 
nitrogenous and non-nitrogenous compounds, and 
each class has a different action in humification 
processes, hence it follows that the humus from the 
green clover must be a complex mixture of both 
nitrogenous and non-nitrogenous bodies. 

The nature of the humus, whether nitrogenous or 
non-nitrogenous, is important. Humus produced from 
sawdust and humus from meat scraps may be taken 
respectively as types of non-nitrogenous and nitroge- 
nous humus. 

106. Value of Humates as Plant Food. — Various 
opinions have been held regarding the actual value, 
as plant food, of this product from partially decayed 
animal and vegetable matter. Humus was formerly 
regarded as composed only of carbon, hydrogen, and 



VALUE OF HUMATES AS PLANT FOOD 9 1 

oxygen, and inasmuch as plants obtain these elements 
from water and from the carbon dioxide of the air, 
no value was assigned to humus. Later, investigators 
added nitrogen to the list, but stated that the nitrogen, 
when combined with the humus and before under- 
going fermentation, was of no value as plant food. 

Recent investigations have proved that the phos- 
phoric acid and other mineral elements combined 
with the organic matter of soils are of value as plant 
food, '7 and it has been demonstrated that crops grown 
on the black soils of Russia obtain a large part of 
their mineral food from organic combinations.^-^. Cul- 
ture experiments have shown that under normal con- 
ditions plants like oats and rye may obtain their min- 
eral food entirely from humate sources. Seeds when 
planted in a mixture of pure sand and neutral humates 
from fertile soils, produced normal plants. In order to 
secure the best conditions for growth, a little lime 
must be present to prevent the formation of humic 
acid, and the organisms found in fertile fields must 
also be introduced. The following example is given 
of oats which were grown when the only supply of 
mineral food was in humate forms. 

Nitrogen and Ash Bi^kments.^' 

In;Six oat In six mature 

seeds. plants. 

Gram. Gram. 

Nitrogen 0.0040 0.0556 

Potash 0.0013 0.0640 

Soda o.ooor 0.0079 

^ Lime 0.0002 0.0249 

Magnesia 0.0005 o.oiio . 

Iron 0.0064 

Phosphoric anhydride 0.0016 0.0960 

Sulphuric anhydride o.ooor 0.0090 

Silicon 0.0026 0.7300 



92 SOILS AND FERTILIZERS 

The fact that plants feed on humate compounds 
and that decaying animal and vegetable matter pro- 
duce humates from the inert potash and phosphoric 
acid of the soil, has an important bearing upon crop 
production, because it indicates a way by which inert 
plant food may be converted into more active and 
available forms. It also explains that stable manure 
is valuable because it makes the inert plant food of the 
soil more available. , 

107. Amount of Plant Food in Humate Forms. — 
In a prairie soil containing 3 y^ per cent, of humus 
there are present 100,000 pounds of humus per acre. 
Combined with this humus there are from 1,000 to 
1,500 pounds each of phosphoric acid and potash. 
Similar soils which have been under long cultivation 
without the restoration of any humus contain from 
300 to 500 pounds each of humic potash and phos- 
phoric acid.^^ A decline in crop-producing power has 
in many cases been brought about by the loss of 
humus. 

108. Loss of Humus. — Loss of humus from soils 
is caused by oxidation and by fires. Any method of 
cultivation which accelerates oxidation reduces the 
humus content. In mau}^ of the western prairie soils 
which have been under continuous grain cultivation 
for thirty years or more, the amount of humus has 
been reduced one-half. Summer fallowing also causes 
a loss of humus. When land is continually under the 
plow, and no manures are used, the humus is rapidly 
oxidized, and there is left, in the soil, organic matter 
which is slow to decay. 

Forest and prairie fires have been very destructive 



PHYSICAL PROPERTIES OF SOILS, ETC. » 93 

to the organic compounds of the soil. A soil from 
Hinckley, Minn., before the great forest fire of 1893, 
showed 1.69 per cent, humus and 0.12 per cent, nitro- 
gen.'^ After the fire there were present 0.41 per cent, 
humus and 0.03 per cent, nitrogen. The forest fire 
caused a loss of 2,500 pounds of nitrogen per acre. 
In clearing new land, particularly forest land, there is 
frequently an unnecessary destruction of humus mate- 
rials. Instead of burning all the vegetable matter 
it would be better economy to leave some in piles for 
future use as manure. When all of the vegetable 
matter has been burned, two or three good crops are 
obtained, but the permanent crop-producing power of 
the land is reduced because of the loss of nitrogen and 
humus. When the vegetable matter has been only 
partially removed,' the crops at first may be smaller, 
but in a few years returns will be greater than if all 
of the vegetable matter had been burned. 

109. Physical Properties of Soils Influenced by 
Humus, — The physical properties of a soil may be 
entirely changed by the addition or the loss of humus. 
The influence of humus upon the weight, color, heat, 
and water-retaining power of soils is discussed in the 
chapter on the physical properties of soils. Soils re- 
duced in humus content have less power of storing up 
water and resisting drought. This fact is illustrated 
in the following table : ^^ 

Per Cent. Water. 

After 10 hours 
exposure in 
In soil. tray, to sun. 

Soil rich in humus (3.75 per cent.) 16.48 6.12 

Adjoining soil poorer in humus (2.50 per cent. ) 12.14 3-94 



94 



SOILS AND FERTILIZERS 



110. Humic Acid. — In the absence of calcium car- 
bonate or other alkaline compounds, the vegetable 
matter ma}^ produce acid products destructive to the 
growth of some crops. The acidity in such cases can 
be readily corrected by the use of lime or wood ashes. 
Acid soils can be distinguished by their action upon 
blue litmus paper. A soil may, hov/ever, give an acid 
reaction and contain a fair amount of lime as a silicate. 
The subject of acid soils and liming is considered in 
Chapter IX. Studies conducted by the Rhode Island 
Experiment Station indicate that the areas of acid 
soils are quite extensive. 

111, Soils in Need of Humus. — Sandy and sandy 






Fig. 20. Humis from old sciL 




Fig. 21. Humis from new soiL 

loam soils that have been cultivated for a number of 
years to corn, potatoes, and small grains without rota- 
tion of crops or the use of stable manures, are deficient 
in humus. Clay soils, as a rule, do not stand in need 
of humus so much as loam and sandv soils. The me- 



DIFFERENT METHODS OF FARMING, ETC. 95 

chanical condition of heavy clays is, however, im- 
proved by the addition of humus-forming material. 
The addition of humus to loam or sandy soils is bene- 
ficial in preventing the soil from drifting, because it 
binds together the soil particles. There are but few 
arable soils, under ordinary cultivation, to which it is 
not safe to add humus-forming materials, either alone 
or. jointly with lime. Ordinary prairie soils, for the 
first ten years after breaking, are usually well supplied. 
Swampy, peaty, and muck soils contain large amounts, 
in fact, they are often overstocked. "Alkali" soils 
are usually deficient in humus. 

112, Active and Inactive Humus. — When soil has 
been long under cultivation, and no manures have 
been used, the nitrogen and mineral matters combined 
with the humus are reduced. The humus from long- 
cultivated fields contains a higher per cent, of carbon 
than that from well-manured or new land ; it is also 
less active because of the higher per cent, of carbon 
which d^es not readily undergo oxidation.'^ 

Humus from Humus from 

new soil. old soil. 

Percent. Percent. 

Carbon 44.12 50.10 

Hydrogen 6.00 4. So 

Oxygen 35.16 33.70 

Nitrogen 8,12 6.50 

Ash 6.60 4.90 

Total humus material.. 5.30 3.38 

113. Influence of Different Methods of Farming upon 
Humus. — The system of farming has a direct effect 
upon the humus content and the composition of the 



96 SOILS AND FKRTILIZKRS 

soil. Where live stock is kept, the manure judiciously 
used, and the crops systematically rotated, the crop- 
producing power of the land is not decreased, as in the 
case of the one-crop system. The influence of differ- 
ent systems of farming upon the humus content and 
other properties of the soil may be observed in the 
following table : ^^ 



" o <u 



tiiS ^^ h^P! .23 a tn c "^-^a 

-513 aw 5?<U P.-S ^ IJ u-j*. ij 



IC 



S " vi " S H 5 

3 iij — H aj ^ S ^ aj ^ rr ( 



Character of soil. ^^ W^ 'g;^ SSIp^^S^ 

Cultivated thirty-five years ; 
rotation of crops and ma- 
nure ; high state of pro- 
ductiveness 70 3.32 0.30 0.04 48 

Originally same as i ; con- 
tinuous grain cropping for 
thirty -five years ; low state 
of productiveness 72 1.80 0.16 o.oi 39 

Cultivated forty-two years ; 
systematic rotation and 
manure ; good state of pro- 
ductiveness • 70 3.46 0.26 0.03 59 

Originally same as 3 ; culti- 
vated thirty-five years ; no 
systematic rotation or ma- 
nure ; medium state of 
productiveness 67 2.45 0.21 0.03 57 



CHAPTER IV 



NITROGEN OF THE SOIL AND AIR, NITRIFICATION, AND 
NITROGENOUS MANURES 

114. Importance of Nitrogen as Plant Food. — 

The illustration (Fig. 22) shows an oat plant which re- 
ceived no nitrogen, while potash, phosphates, lime, and 
all other essential elements of plant food 
were liberally supplied. Observe the pe- 
culiar and restricted growth, with but 
limited root development. The leaves 
were yellowish. 

In the absence of nitrogen a plant 
makes no appreciable growth. With only 
a limited supply, a plant begins its growth 
in a normal way, but as soon as the avail- 
able nitrogen is used up, the lower and 
smaller leaves begin gradually to die 
down from the tips, and all of the plant's 
energy is centered in one or two leaves. 
In one experiment when only a small 
amount of nitrogen was supplied, the plant 
struggled along in this way for about nine 
weeks, making a total growth of but six 
and one-half inches.'^ Just at the critical point 
when the plant was dying of nitrogen starvation, 
a few milligrams of calcium nitrate were given. In 
thirty-six hours the plant showed signs of renewed 
life, the leaves assumed a deeper green, a new growth 
was begun, and finally four seeds were produced. 

(7) 




Fig. 22. 
Oat plant 
grown with- 
out nitrogen. 



98 SOILS AND FERTILIZERS 

During the time of seed formation more nitrogen was 
added, but with no beneficial result. All of the es- 
sential elements for plant growth were liberally pro- 
vided, except nitrogen, which was very sparingly sup- 
plied at first, until near the period of seed formation, 
when it was more liberally supplied. 

When plants have reached a certain period in their 
development, and have been starved for want of nitro- 
gen, the later application of this element does not 
produce normal growth, as the energies of the plant 
have been used up in searching for food. Nitrogen, 
as well as potash, lime, and phosphoric acid, are all 
necessary while plants are in their first stages of 
growth. 

In the case of wheat, nitrogen is assimilated more 
rapidly than are any of the mineral elements. Before 
the plant heads out, over 85 per cent, of the total 
nitrogen required has been taken from the soil.^^ 
Corn also takes up all of its nitrogen from four to 
five weeks before the crop matures. Flax takes up 75 
per cent, of its nitrogen during the first fifty da3^s of 
growth. 3^ 

Nitrogen is demanded by all crops. It forms the 
chief building material for the proteids of plants. In 
the absence of a sufficient amount of nitrogen, the 
rich green color is not developed ; the foliage is of a 
yellowish tinge. Nitrogen is one of the constituents 
of chlorophyl, the green coloring-matter of plants, 
hence when there is a lack of nitrogen only a limited 
amount of chlorophyl can be produced. Plants with 



ATMOSPHKRIC NITROGEN 99 

large, well-developed leaves of a rich green color are 
not suffering for nitrogen. Nitrogenous fertilizers 
have a tendency to produce a luxurous growth of 
foliage, deep green in color. 
ATMOSPHERIC NITROGEN AS A SOURCE OF PLANT FOOD 

115. Early Views. — In addition to carbon, hydro- 
gen, and oxygen, which form the organic compounds 
of plants, it was known as early as the beginning of 
the present century that plants also contained nitrogen. 
The sources of the carbon, hydrogen, and oxygen for 
crop purposes were much easier to determine and 
understand than the sources of nitrogen. Priestley, 
the discoverer of oxygen, believed that the free nitro- 
gen of the air was a factor in supplying plant food. 
De Saussure arrived at just the opposite conclusion. 
Neither of these assumptions were convincing because 
methods of chemical analysis had not yet been suffi- 
ciently perfected to solve the question. 39 

116. Boussingault^s Experiments. — Boussingault 
was the first to make a careful study of the subject. 
In a prepared soil, free from nitrogen, and containing 
all of the other elements necessary for plant growth, 
he grew clover, wheat, and peas, carefully determining 
the nitrogen in the seed. The plants were allowed 
free access to the air, being simply protected from 
dust, and were watered with distilled water. But 
little growth was made. At the end of two months 
the plants were submitted to chemical analysis, and 
the amount of nitrogen present was determined. 

His first results are given in the following table : 4° 
LofG. 



lOO SOILS AND FERTILIZERS 

Nitrogen. 

In seed sown. In plant. Gain. 

Gram. Gram. Gram. 

Clover, 2 mos o. ii 0.12 o.oi 

" 3 " 0.114 0.156 0,042 

Wheat, 2 " 0.043 0-04 — 0.003 

" 3 " 0.057 0.06 0.003 

Peas, 2 " 0.047 o. 10 0.053 

Boussingault concluded that when plants in a sterile 
soil were exposed to the air, there was with some a 
slight gain of nitrogen, but the amount gained from 
atmospheric sources was not suffi- 
cient to feed the plant and allow it 
to reach full maturity. By many ( B 

these results were not accepted as 
conclusive. 

Fifteen years later (1853) Bous- 
singault repeated his experiments, 
but in a different way. The plants 
were now grown in a large carboy I \ ^^ ^'y 
with a limited volume of air so as to \ % 
cut off all sources of combined nitro- 
gen, as ammonia. . By means of a p- 
second glass vessel (d, Fig. 23) the plants grown 
carboy was kept liberally supplied in carboy, 
with carbon dioxide, so that plant 
growth would not be checked for lack of this material. 
When experiments were carried on in this way using a 
fertile soil, the plants reached full maturity, but when 
a soil free from nitrogen was used, plant growth was 
soon checked. A general summary of this work is 
given in the following table :^° 




ATMOSPHERIC NITROGEN lOI 

Nitrogen. 

In seeds. In plant. I,oss. 

Gram. Gram. Gram. 

Dwarf beans o. looi 0.0977 —0,0024 

Oats 0.0109 0.0097 — 0.0012 

White lupines 0.2710 0.2669 — 0.0041 

Garden cress 0.0013 0.0013 

These experiments show that with a sterilized soil, 
and all sources of combined atmospheric nitrogen cut 
off, the free nitrogen of the air takes no part in the 
food supply of the plant. 

In 1854 Boussingault again repeated his experi- 
ments on nitrogen assimilation. This time he grew 
the plants in a glass case so constructed that there was 
a free circulation of air from which all combined nitro- 
gen had been removed. These experiments were 
similar to his second series; the plants, however, 
were not grown in a limited volume of air. The 
results obtained showed that the free nitrogen of 
the air, under the conditions of the experiment, took 
no part in the food supply of the plants. If anything, 
there was less nitrogen recovered in the dwarfed 
plants than there was in the seed sown. 

117. Vine's Results. — About the same time Ville 
carried on a series of experiments of like nature, but 
in a different way, and arrived at just the "opposite 
conclusions. In short, his experiments indicated that 
plants are capable of making liberal use of the free 
nitrogen of the air for food purposes. The directly 
opposite conclusions of Boussingault and Ville, led to 
a great deal of controversy. The French Academy of 
Science took up the question, and appointed a com- 



I02 SOILS AND FERTILIZERS 

mission to review the work of Ville. The commis- 
sion consisted of six prominent scientists. They 
reported that "M. Ville's conclusions are consistent 
with his labor and results." ^9 

ii8. Work of Lawes and Gilbert. — A little later 
Lawes and Gilbert carried on such extensive ex- 
periments under a variety of conditions as to remove 
all doubt regarding the question. Plants were grown 
in sterilized soils, in prepared pumice stone, and in 
soils with a limited and known quantity of nitrogen 
beyond that contained in the seed. Different kinds 
of plants were experimented with. The work was 
carried on with the utmost care and with apparatus 
so constructed as to eliminate all disturbing factors. 
The results in the aggregate clearly indicate that 
plants, when acting in a sterile medium, are unable 
to make use of the free nitrogen of the air for the pro- 
duction of organic matter. 39. 

119. Atwater's Experiments. — Atwater carried on 
similar experiments in this country.^^ His results 
indicate that when seeds germinate they lose a 
small part of their nitrogen, and that when legumes 
are grown in a sterile soil, but are subsequently ex- 
posed to the air, a fixation of nitrogen may occur. 

120. Field and Laboratory Tests. — By a five years' 
rotation of clover and other leguminous plants, Lawes 
and Gilbert found that a soil gained from two to four 
hundred pounds of nitrogen per acre, in addition to 
that removed in the crop, while land which produced 
wheat continuously had gradually lost nitrogen. The 



ATMOSPHERIC NITROGEN 1 03 

amount in the subsoil remained nearly the same. All 
of these facts plainly indicated that crops like clover 
had the power of gaining nitrogen from unknown 
sources. The results of prominent German agricul- 
turists led to the same conclusion. It was known 
that wheat grown after clover gave as good results as 
the use of nitrogenous manures for the wheat, but for 
many years this fact was unexplained. 

Laboratory experiments with sterilized soils do not 
represent the normal conditions of growing crops 
where all of the bacteriological agencies of the soil 
the air, and the plant, are free to act. Experiments 
have shown that these agencies have an important 
bearing upon plant growth. 

In the work of the different investigators prior to 
1888, plants were grown mginly in sterilized soils, and 
under such conditions they were unable to make use 
of the free nitrogen of the air, except when subse- 
quently innoculated from the air. 

121. Hellriegers Experiments. — Hellriegel grew 
leguminous plants in nitrogen-free soils. One set of 
plants was watered with distilled water, while another 
had in addition small amounts of leachings from an 
old loam field. The plants watered with distilled 
water alone, made but little growth, while those 
watered with the loam leachings reached full matur- 
ity and contained something like a hundred times 
more nitrogen than was in the seed sown. The dark 
green color was also developed, showing the presence 
of a normal amount of chlorophyl. The roots of the 



i04 SOILS AND FERTILIZERS 

plants had well-formed swellings or nodules, while 
those that were watered with distilled water alone had 
none. The loam leachings contained only a trace of 
nitrogen. 42 

122. Experiments of Wilfarth.— Experiments by 
Wilfarth give more exact data regarding the amount 
of nitrogen taken from the air. Two plots of lupines 
were grown, one was watered with distilled water, 
while the other received in addition leachings from 
an old lupine field. 

Watered with distilled water. Watered with soil leachings. 

Drj^ matter. Nitrogen. Dry matter. Nitrogen. 



Grams. 


Grams. 


Grams. 


Grams. 


0.919 


0.015 


44.72 


1.099 


0.800 


0.014 


45.61 


1. 153 


0.921 


0.013 


44.48 


1. 195 


1. 02 1 


0.013 


42.45 


1.337 



These experiments have been verified by many 
other investigators until the fact has been established 
that leguminous plants may, through the agency of 
micro-organisms, make use of the free nitrogen of the 
air. The work of Hellriegel was not accidental but 
the result of careful and systematic investigation. As 
early as 1863 he observed that clover would develop 
along the roadway in sand in which there was scarcely 
a trace of combined nitrogen. 

123. Composition of Root Nodules. — The root 
nodules referred to, are particularly rich in nitrogen. 
In one experiment, the light-colored and active ones 
contained 5.55 per cent., while the dark-colored and 
older ones contained 3.21 per cent. The entire 
nodules of the root, both active and inactive, con- 



ATMOSPHERIC NITROGEN 105 

tained 4.60 per cent, nitrogen. The root itself con- 
tained 2.21 per cent.43 

The root nodules also contain definite and charac- 
teristic micro-organisms, and it was the spores of these 
organisms that were present in the soil extract in both 
HellriegePs and Wilfarth's experiments. In the ster- 
ilized soils they were not present. These organisms 
found in root nodules, are the essential agents which 
aid in the fixation of the free nitrogen of the air, and 
in its ultimate use as plant food. Experiments have 
shown that these organisms are capable of being 
propogated in nutritive media, separate from clover 
roots.^7 

124. Nitrogen in the Root Nodules Returned to 
the Soil. — Ward has shown that when clover roots 
decay, the organisms and nitrogen present in the 
nodules are distributed within the soil. 3^ Hence, 
whenever a leguminous crop is raised, nitrogen is 
added to the soil, instead of being taken away, as in 
the case of a grain crop. The amount of nitrogen 
per acre returned to the soil by a leguminous crop as 
clover, varies with the growth of the crop. In the 
roots of a clover crop a year old there are present 
from 20 to 30 pounds of nitrogen per acre, while in 
the roots and culms of a dense clover sod, two or three 
yqars old, there may be present 75 pounds or more of 
nitrogen. Peas, beans, lucern, cow peas, and all 
legumes, possess the power of fixing the free nitrogen 
of the air by means of micro-organisms. The micro- 
organisms associated with one species, as clover, differ 



I06 SOILS AND FERTILIZERS 

from those associated with another, as lucern. The 
amount of nitrogen which the various legumes return 
to the soil is variable. Hellriegel's results are of the 
greatest importance to agriculture, because they show 
how the free nitrogen of the air can be utilized in- 
directly as food by crops unable to appropriate it for 
themselves. 

THE NITROGEN COMPOUNDS OF THE SOIL 

125. Origin of the Soil Nitrogen. — The nitrogen of 
the soil is derived chiefly from the accumulated re- 
mains of animal and vegetable matter. The original 
source of the soil nitrogen, that is the nitrogen which 
furnished food to support the vegetation from which 
our present stock of soil nitrogen is obtained, was 
probably the free nitrogen of the air. All of the ways 
in which the free nitrogen of the air has been made 
available to plants of higher orders which require 
combined nitrogen, are not known. It is supposed, 
however, that this has been brought about by the 
workings of lower forms of plant life, and by micro- 
organisms. Whatever these agencies have been they 
do not appear to be active in a soil under high culti- 
vation, because the tendency of ordinary cropping is 
to reduce the supply of soil nitrogen. 

126. Organic Nitrogen of the Soil. — In ordinary 
soils the nitrogen is present mainly in organic forms 
combined with the carbon, hydrogen, and oxygen, 
and to a less extent with the mineral elements, form- 
ing nitrates. The organic forms of nitrogen, it is 
generally considered, are incapable of supplying plants 



NITROGEN COMPOUNDS OF THE SOIL IO7 

with nitrogen for food purposes until the process 
known as nitrification takes place. The nitrogenous 
organic compounds in cultivated soils are derived 
mainly from the undigested protein compounds of 
manure and from the nitrogenous compounds in crop 
residues, and are present mainly as insoluable pro- 
teids.^5 When decomposition occurs, amides, organic 
salts, and other allied bodies are without doubt pro- 
duced as intermediate products before nitrification 
takes place. The organic nitrogen of the soil may be 
present in exceedingly inert forms similar to leather. 
In fact, in many peaty soils there are large amounts of 
inactive organic compounds rich in nitrogen. In 
other soils the nitrogen is present in less complex 
forms. The organic nitrogen of the soil may vary in 
complexity from forms like the nitrogen of urea to 
forms like that of peat. 

127. Amount of Nitrogen in Soils. — The fertility 
of any soil is dependent, to a great extent, upon the 
amount and form of its nitrogen. In soils of the 
highest degree of fertility there is usually present 
from 0.2 to 0.3 per cent, of total nitrogen, equivalent 
to from 7,000 to 10,000 pounds per acre to the depth 
of one foot. Many soils of good crop-producing power 
contain as low as 0.12 per cent. There is usually two 
or three times more nitrogen in the surface soil than 
in the subsoil. In sandy soils which have been 
allowed to decline in fertility, there may be less than 
0.04 per cent. Of the total nitrogen in soils there is 
rarely more than 2 per cent, at any one time, in forms 



I08 SOII.S AND FBRTII.IZBRS 

available as plant food/^ A soil with 5,000 pounds 
of total nitrogen per acre would contain about 100 
pounds of available nitrogen, of which only a part 
comes in contact with the roots of crops. Hence, it 
is that a soil may contain a large amount of total 
nitrogen, and yet be deficient in available nitrogen. 

128. Amount of Nitrogen Removed in Crops. — 
The amount of nitrogen removed in crops ranges from 
25 to 100 pounds per acre depending upon the nature 
of the crop. It does not necessarily follow that the 
crop which removes the largest amount of nitrogen 
leaves the land in the most impoverished condition. 
Wheat and other grains, while they do not remove 
such a large amount of nitrogen in the crop, leave the 
soil more exhausted than if other crops were grown. 
This, as will be explained, is caused by the loss of 
nitrogen from the soil in other ways than through 
the crop.3^ 

Pounds of nitrogen 
per acre. 

Wheat, 20 bushels 25 

Straw, 2,000 pounds 10 

Total 35 

Barley, 40 bushels 28 

Straw, 3,000 pounds 12 

Total 40 

Oats, 50 bushels 35 

Straw, 3,000 pounds 15 

Total 50 

Flax, 15 bushels 39 

Straw, 1,800 pounds 15 

Total 54 

Potatoes, 150 bushels 40 

Corn, 65 bushels 40 

Stalks, 3,000 pounds 35 

Total 75 



NITROGEN COMPOUNDS OF THK SOIL I09 

129. Nitrates and Nitrites.— The amount of nitro- 
gen in the form of nitrates and nitrites, varies from 
mere traces to 150 pounds per acre. Calcium nitrate 
is the usual form met with, especially in soils which 
are sufficiently supplied with calcium carbonate to 
allow nitrification to progress rapidly. Nitrates and 
nitrites are the most valuable forms of nitrogen for 
plant food. Both are produced from the organic 
nitrogen of the soil. A nitrate is a compound com- 
posed of a base element as sodium, potassium, or cal- 
cium, combined with nitrogen and oxygen. A nitrite 
contains less oxygen than a nitrate. 

Potassium nitrate, KNO^, sodium nitrate, NaNO , 
and calcium nitrate, Ca(NO^)^, are the nitrates which 
are of most importance in agriculture. The nitrites, 
as potassium nitrite, KNO^, are present to a less 
extent than the nitrates. Nitrates and nitrites are 
found in surface well waters contaminated with 
animal and vegetable matter. Many well waters 
possess some material value as a fertilizer on account 
of the nitrates, nitrites, and decaying animal and 
vegetable matters which they contain. 

130. Ammonium Compounds of the Soil. — The 

amount of ammonium compounds in a soil is usually 
less than the amount of nitrates and nitrites. The 
sources of the ammonium compounds are, rain-water 
and the organic matter of the soil. The ammonium 
compounds are all soluble and readily undergo fixa- 
tion. See Section 207. They cannot accumulate in 
arable soils, because of nitrification. They are usually 



no SOILS AND FERTILIZERS 

found in surface well waters. In the soil, the 
ammonium compounds may be oxidized and form 
nitrates. Compounds, as ammonium chloride or am- 
monium carbonate, if present in a soil in excessive 
amounts, will destroy vegetation in a way similar to 
the alkaline compounds in alkaline soils. 

131. Nitrogen in Rain- Water and Snow. — The 

amount of nitrogen which is annually returned to the 
soil in the form of ammonium compounds dissolved 
in rain-water and snow, is equivalent to from 2 to 3 
pounds per acre. At the Rothamsted experiment 
station the average amount for eight years was 3.37 
pounds.'^^ When a soil is rich in nitrogen the gain 
from rain and snow is only a partial restoration of 
that which has been given off from the soil to the air 
or lost in the drain waters. The principal form of 
the nitrogen in rain water is ammonium carbonate 
which is present in the air to the extent of about 22 
parts per million parts of air. 

132. Ratio of Nitrogen to Carbon in the Organic 
Matter of Soils. — In some soils the organic matter is 
more nitrogenous than in others. In those of the 
arid regions the humus contains from 15 to 20 per 
cent, of nitrogen, while soils from the humid regions 
contain 4 to 6 per centos In some soils the ratio of 
nitrogen to carbon may be i to 6, while in others it 
may be i to 18, or more. That is, in the organic 
matter of some soils there is i part of nitrogen to 6 
parts of carbon, while in others the organic matter 
contains i part of nitrogen to 18 parts of carbon. In 



NITROGEN COMPOUNDS OF THE SOIL I I I 

a soil where there exists a wide ratio between the 
nitrogen and carbon, it is believed that the conditions 
for supplying crops with available nitrogen are un- 
favorable. 

133. Losses of Nitrogen from Soils. — When a soil 
rich in nitrogen is cultivated for a number of years 
exclusively to grain crops there is a loss of nitrogen 
exceeding the amount removed in the crop, caused by 
the rapid oxidation of the organic matter of the soil. 
Experiments have shown that when a soil of average 
fertility is cultivated continually to grain, for every 
25 pounds of nitrogen removed in the crop there 
is a loss of 146 pounds from the soil due to the de- 
struction of the organic matter.'^ In general, any 
system of cropping which keeps the soil continually 
under the plow, results in decreasing the nitrogen. 
When a soil is rich in nitrogen the greatest losses 
occur ; when poor in nitrogen there is relatively less 
loss. When a soil rich in nitrog^en is griven arable 
culture the oxidation of the organic matter and the 
losses of nitrogen take place rapidly. The longer a 
soil is cultivated, the slower the oxidation of the 
humus and the relative loss of nitrogen. 

134. Gain of Nitrogen in Soils. — When arable land 
is permanently covered with vegetation, there is a 
gain of nitrogen. Pasture land contains more nitro- 
gen than cultivated land of a similar character ; also 
in meadow land, there is a tendency for the nitrogen 
to increase. These facts are well illustrated in the 
investigations of Lawes and Gilbert, at Rothamsted.44 



112 SOII.S AND FERTILIZERS 

Age of Pasture Nitrogen 

Years. Per Cent. 

Arable land 0.14 

Barn-field pasture 8 0.151 

Apple-tree pasture 18 0.174 

Meadow 21 0.204 

Meadow 30 0.241 

After deducting the amount of nitrogen in the manure 
added to the meadow land, the annual gain of nitrogen 
was more than 44 pounds per acre. 

Another source of gain of nitrogen is the fixation of 
the free nitrogen of the air by the growth of clover 
and other leguminous crops. If a soil is properly 
manured and cropped the amount of nitrogen may be 
increased. A rotation of wheat, clover, wheat, oats, and 
corn with manure will leave the soil at the end of the 
period of rotation in better condition as regards nitro- 
gen than at the beginning. These facts are illustrated 
in the following table : ^^ 

Continuous Wheat Cui^ture — 

Nitrogen in soil at beginning of experiment 0.221 per cent. 

Nitrogen at end of 5 years continuous wheat culti- 
vation 0-I93 " " 

l/oss per annum per acre (in crop 24.5, soil 146.5). 171 pounds. 

Rotation of Crops — 

Nitrogen in soil at beginning of rotation 0.221 per cent. 

Nitrogen at close of rotation 0.231 " " 

Gain to soil per annum per acre 61 pounds. 

Nitrogen removed in crops per annum 44 " 

It is to be regretted that in the cultivation of large 
areas of land to staple ciops as wheat, corn, and cotton, 
the methods of cultivation followed are such as to de- 
crease the nitrogen content and crop producing power 
of the soil when this could be prevented. 



NITRIFICATION 

135. Former Views Regarding Nitrification. — The 

presence of nitrates and nitrites in soils was formerly 
accounted for by oxidation. The theory was held 
that the production of nascent nitrogen by the de- 
composition of organic matter caused a union be- 
tween the oxygen of the air and the nitrogen of the 
organic matter. Fermentation studies by Pasteur led 
him to believe that possibly the formation of nitric 
acid in the soil might be due to fermentation. It was, 
however, 15 years later before the French chemists, 
Schlosing and Miintz, established the fact that nitrifi- 
cation is produced by a living organism. 

136. Nitrification Caused by Micro-organisms. — 
Nitrification is the process by which nitrates or 
nitrites are produced in soils, by the workings of or- 
ganisms. Nitrification results in changing the com- 
plex organic nitrogen of the soil to the form of 
nitrates or nitrites. It is the process by which the 
inert nitrogen of the soil is rendered available as crop 
food. The organisms which carry on the work of 
nitrification have been isolated and studied by War- 
ington, and by Winogradsky. 

137. Conditions Necessary for Nitrification are : 

1. Food for the nitrifying organisms. 

2. A supply of oxygen. 

3. Moisture. 

4. A favorable temperature. 

5. Absence of strong sunlight. 

6. The presence of some basic compound. 

(8) 



114 SOILS AND FERTILIZERS 

In order to allow nitrification to proceed, all of these 
conditions must be satisfied. The process is fre- 
quently checked because some of the conditions, as 
presence of a basic compound, are unfulfilled. 

138. Food for the Nitrifying Organisms. — All liv- 
ing organisms require food, and one of the food re- 
quirements of the nitrifying organism is a supply of 
phosphates. In the absence of phosphoric acid, 
nitrification cannot take place. The change which 
the phosphoric acid undergoes in serving as food for 
the nitrifying organism is unknown, but it doubtless 
makes the phosphoric acid more available as plant 
food9\ The principal organic food of the nitrifying 
organism is the organic matter of the soil. Organic 
matter, only when incorporated with soil, can serve as 
food for the nitrifying organism. In the presence of 
a large amount of organic matter, as in a manure 
pile, nitrification does not take place. The process 
can take place only when the organic matter is largely 
diluted with soil. Under favorable conditions nitrify- 
ing organisms may take all of their food in inorganic 
forms ; that is, nitrification may take place in the ab- 
sence of organic matter provided the proper mineral 
food be supplied. When growth under such condi- 
tions takes place the organisms assimilate carbon 
from the combined carbon of the air, and produce 
organic carbon compounds. An organism, working 
in the absence of sunlight and unprovided with 
chlorophyl, may construct organic carbon com- 
pounds.4^ The nitrification which takes place in the 
absence of nitrogeneous organic matter is of too 



NITRIFICATION II 5 

limited a character to supply growing crops with all 
of their available nitrogen. For general crop pro- 
duction the organic matter of the soil is the source of 
the nitrogen which undergoes the nitrification process, 
and which furnishes food for the nitrifying organisms. 

139. Oxygen Necessary for Nitrification. — The 
second requirement for nitrification is an adequate 
supply of oxygen. The nitrification organism belongs 
to that class of ferments (aerobic) which requires oxy- 
gen for existence. Oxygen is present as one of the 
elements in the final product of nitrification as in cal- 
cium nitrate, Ca(NO )^. In the absence of oxygen 
the nitrification process is checked. When soils are 
saturated with water, the process cannot go on for 
want of oxygen. Cultivation, particularly of clay 
soils, favors nitrification increasing the supply of 
oxygen in the soil. 

140. Moisture Necessary for Nitrification. — Nitri- 
fication cannot take place in a soil deficient in mois- 
ture. x\s in all fermentation processes, so with nitri- 
fication, moisture is necessary for the chemical changes 
to take place. In a very dry time nitrification is ar- 
rested for want of water. Water is as necessary to 
the growth and development of the living organism 
which carries on the work of nitrification, as it is to 
the life of a plant of higher order. 

141. Temperatures Favorable for Nitrification. — 
The most favorable temperatures for nitrification are 
between 12° C. (54° F.) and 2,7° C. (99° F.). It may 



Il6 SOIIvS AND FERTILIZERS 

take place at as low a temperature as 3° or 4° C. 
(37° and 39° F.); at 50° C. (122° F.) it is feeble, 
while at 55° C. (130° F.) there is no action. ^4. In 
northern latitudes nitrification is checked during the 
winter, while in southern latitudes this change takes 
place during the entire year. As a result many soils 
in southern latitudes contain less nitrogen than soils 
in northern latitudes where fermentation and leaching 
of nitrates is checked by climatic conditions. Crops 
which require their nitrogen early in the growing 
season are frequently placed at a disadvantage be- 
cause there is less available nitrogen in the soil at 
that time than later. 

142. Strong Sunlight Checks Nitrification. — Nitri- 
fication cannot take place in strong sunlight ; it pre- 
vents the action of all organisms of this class. In 
fallow land there is no nitrification at the surface but 
immediately below where the sunlight is excluded by 
the surface soil, it is most active. In a cornfield it is 
more active than in a compacted fallow field. 

143. Base-forming Elements Essential for Nitrifi- 
cation. — The presence of some base-forming element 
to combine with the nitric acid produced is a neces- 
sary condition for nitrification, and for this purpose 
calcium carbonate is particularly valuable. The ab- 
sence of basic materials is one of the frequent causes 
of non-nitrification. In acid soils, the process is 
checked for the want of proper basic material. The 
organisms which carry on the work cannot exist in 
strong acid or alkaline solution, consequently in such 
soils nitrification cannot take place.^7 



NITRIFICATION II 7 

144. Nitrous Acid Organisms. — There are at least 
two nitrifying organisms in the soil; one produces 
nitrates and the other nitrites or nitrous acid. It is 
believed that the process takes place in two stages, 
the first being performed by the nitrous organism, 
and the process being completed by the nitric organ, 
ism. Warington says that " both organisms are 
present in the soil in enormous numbers, — and the 
action of the two organisms proceeds together, as the 
conditions are favorable to both." 

145. Ammonia-producing Organisms. — There are 
also present in the soil organisms which have the 
power of producing ammonia from proteid bodies. 
The ammonium compounds produced are acted upon 
by the nitrifying organisms and readily undergo nitri- 
fication. ^^ 

146. Denitrification is just the reverse of the nitri- 
fication process, and is the result of the workings of a 
class of organisms which feed upon the nitrates form- 
ing free nitrogen which is liberated as a gas. One of 
the conditions for denitrification is absence of air, as 
the organisms belong to the anaerobic class. Denitri- 
fication readily takes place in soils saturated with 
water, and where the soil is compacted so that air is 
practically excluded. -^^ 

14V. Number and Kinds of Organisms in Soils. ^ 

In addition to the micro-organisms which carry on the 
work of nitrification, denitrification, and ammonifica- 
tion, there are a great many others, some of which are 



Il8 SOILS AND FERTILIZERS 

beneficial while others are injurious to crop growth. 
It has been estimated that in a gram of an average 
sample of soil there are from 60,000 to 500,000 bene- 
ficial and injurious micro-organisms/^ There are pro- 
duced from many crop residues, by injurious ferments, 
chemical products which may be destructive to crop 
growth. Flax straw, for example, when it decays in 
the soil forms chemical products which are destructive 
to a succeeding flax crop. 

A moist soil, rich in organic matter, and containing 
various salts, may form the medium for the propaga- 
tion of all classes of organisms. Sewage-sick soils 
clover-sick soils, and flax-diseased lands are all the re- 
sults of bacterial diseases. Many of the organisms 
which are the cause of such diseases as typhoid fever, 
and cholera, may propagate and develop in a moist 
soil under certain conditions, and then find their 
way through drain water into surface wells, and cause 
these diseases to spread. 

148. Products Formed by Soil Organisms. — In 
considering the part which micro-organisms take in 
plant growth, as well as in all similar processes, there 
are two phases to be considered: (i) the action of the 
organism itself, and (2) the chemical action of the pro- 
duct of the organism. In the case of nitrification, the 
action of the organism brings about a change in the 
composition of the organic matter, producing nitric 
acid which is merely a product formed as a result of 
the action of the organism. The nitric acid then acts 
upon the soil, producing nitrates. In the case of soils 
rich in organic matter, the fermentation changes which 



NITRIFICATION Ug 

take place during humification result in the produc- 
tion of acid products. This is simply the result of 
the action of the ferments. The acids then act upon 
the soil bases and produce humates or organic salts. 
In many fermentation changes there is first the pro- 
duction of some chemical compound, and then the 
action of this compound upon other bodies. In ren- 
dering plant food available, as in nitrification and 
humification, it is the final product, and not the first 
product of the organism, which is of value. 

149. Inocculating Soils with Organisms.— Ingrow- 
ing leguminous crops on soils where they have never 
before been produced, it has been proposed to supply 
the essential organisms which assist the crops to ob- 
tain their nitrogen. For example, if clover is grown 
on new land, the soil is liable to be deficient Tn the 
organisms which assist in the assimilation of nitrogen 
and which are present in the root nodules of the 
plant. If these organisms are supplied, better condi- 
tions for growth exist. Some soils are benefitted by 
inocculation, while others are not. The extent to 
which it is necessary to inocculate different soils with 
organisms for the assimilation of nitrogen, has not yet 
been determined by actual field experiments. 

150. Loss of Nitrogen by Fallowing Rich Lands.— 

Summer fallowing creates conditions favorable to 
nitrification. A fallow is beneficial to a succeeding 
crop because of the nitrogen which is rendered avail- 
able. If a soil is rich in nitrogen and lime, summer 
fallowing causes the production of more nitrates than 



I20 SOILS AND FERTILIZERS 

can be retained in the soil. The crop utilizes only a 
part of the nitrogen rendered available, the rest being 
lost by drainage, ammonification, and denitrification. 
Hence the available nitrogen is increased while the 
total nitrogen is greatly decreased. ^^ 

Soil before Soil after 

fallowing. fallowing. 

Total nitrogen o. 154 o. 142 

Soluble nitrogen 0.002 0,004 

The gain of 0.002 per cent, of soluble nitrogen was 
accompanied by a loss of 0.012 per cent, of total 
nitrogen. For every pound of available nitrogen 
there was a loss of six pounds. Bare fallowing of 
land should not be practiced, except occasionally to 
destroy weeds or insects, as it results in permanent 
injury to the soil. 

151. Influence of Plowing upon Nitrification. — 

In a rich prairie soil nitrification goes on very rapidly. 
This is one reason why shallow plowing on new 
breaking gives better results than deep plowing. 
Deep plowing at first, causes nitrification to take place 
to such an extent that the crop is overstimulated in 
growth, due to an excess of available nitrogen. Deep 
plowing and thorough cultivation aid nitrification. 
The longer a soil has been cultivated, the deeper and 
more thorough must be the cultivation. 

Early fall plowing leaves more available nitrogen 
at the disposal of the crop than late fall plowing. 
Nitrification takes place only near the surface. Hence 
when late spring plowing is practiced there is brought 
to the surface raw nitrogen, while the available nitro- 



NITROGENOUS MANURES 121 

gen has been plowed under, and is beyond the reach 
of the young plants when they require the most help 
in obtaining food. The various methods of cultiva- 
tion as deep and shallow plowing, spring and fall 
plowing, and surface cultivation have as much influ- 
ence upon the available nitrogen supply of crops as 
upon the water supply. The saying that cultivation 
makes plant food available is particularly true of the 
element nitrogen, the supply of which is capable of 
being increased or decreased to a greater extent than 
that of any other element. 

NITROGENOUS MANURES 

152. Sources of Nitrogenous Manures. — The mate- 
rials used for enriching soils with nitrogen, to promote 
crop growth, may be divided into two classes : (i) 
organic nitrogenous manures, (2) mineral nitrogenous 
manures. Each of these classes has a different value 
as plant food, and in fact there are marked differences 
in fertilizer value between materials belonging to the 
same class. The nitroo^enous oro-anic materials used 
for fertilizing purposes are ; dried blood, tankage, 
meat scraps and flesh meal, fish offal, cottonseed meal, 
and leguminous crops as clover and peas. The nitro- 
gen in these substances is principally in the form of 
protein. When peat and muck are properly used 
they .also may be classed among the nitrogenous 
manures. The mineral nitrogenous manures are 
nitrates, as sodium nitrate, and ammonium salts, as 
ammonium sulphate. 

123. Dried Blood. — This is obtained by drying 



122 SOILS AND FERTILIZERS 

the blood and debris from slaughter-houses. Fre- 
quently small amounts of salt and slaked lime are 
mixed with the blood. It is richest in nitrogen of 
any of the organic manures. When thoroughly dry 
it may contain 14 per cent, of nitrogen. As usually 
sold, it contains from 10 to 20 per cent, of water, and 
has a nitrogen content of from 9 to 13. Dried blood 
contains only small amounts of other fertilizer ele- 
ments ; it is strictly a nitrogenous fertilizer, readily • 
yielding to the action of micro-organisms and to nitri- 
fication. On account of its fermentable nature, it is 
a quick-acting fertilizer, and is one of the most valu- 
able of the organic materials used as manure. It 
gives the best returns when used on an impoverished 
soil to aid crops in the early stages of growth, before 
the inert nitrogen of the soil becomes available. 
Dried blood may be applied as a top dressing on grass 
land, and it is also an excellent form of fertilizer to 
use on many garden crops, but it should not be placed 
in direct contact with seeds, as it will cause rotting, 
nor should it be used in too large amounts. Three 
hundred pounds per acre is as much as should be ap- 
plied at one time. When too much is used losses of 
nitrogen may occur by leaching and by denitrification. 
It is best applied directly to the soil, as a top dressing 
in the case of grass, or near the seeds of garden crops, 
and not mixed with unslaked lime or wood ashes, but 
each should be used separately. As all plants take up 
their nitrogen early in their growth, nitrogenous fer- 
tilizers as blood should be applied before seeding or 
soon after. An application of dried blood to partially 



NITROGENOUS MANURES 1 23 

matured garden crops will cause a prolonged growth 
and very late maturity. 

Storer gives the following directions for preserving 
any dried blood produced upon farms.^^ "The blood 
is thoroughly mixed in a shallow box with 4 or 5 
times its weight of slaked lime. The mixture is cov- 
ered with a thin layer of lime and left to dry out. It 
will keep if stored in a cool place, and may be applied 
directly to the land or added to a compost heap." 

The price per pound of nitrogen in the form of 
dried blood can be determined from the cost and the 
analysis of the material. A sample containing 9 per 
cent, of nitrogen and selling for $28 per ton is equiva- 
lent to 15.55 cents per pound for the nitrogen (2000 X 
0.09 = 180. $28.00 -=- 180 = 15.55 cents). 

154. Tankage is composed of refuse matter as bones, 
trimmings of hides, hair, horns, hoofs and some blood. 
The fat and gelatin are, as a rule, first removed by 
subjecting the material to superheated steam. This 
miscellaneous refuse, after drying, is ground and 
sometimes mixed with a little slaked lime to prevent 
rapid fermentation. 

Tankage contains less nitrogen but more phosphoric 
acid than dried blood. Owing to its miscellaneous 
nature, it is quite variable in composition, as the fol- 
lowing analyses of tankage from the same abattoir at 
different times show.^'^ 

First year. Second year. Third year. 

Moisture 10.5 9.8 10.9 

Nitrogen 5.7 7.6 6.4 

Phosphoric acid 12.2 10.6 11. 7 



124 SOILS AND FERTILIZERS 

As a general rule, tankage contains from 5 to 8 per 
cent, of nitrogen and from 6 to 14 per cent, of phos- 
phoric acid. It is much slower in its action than 
dried blood, and supplies the crop with both nitrogen 
and phosphoric acid. Tankage is a valuable form of 
ferlizer to use for garden purposes. It may also be 
used as a top dressing on grass lands, and may be 
spread broadcast on grain lands. It is best to apply 
the tankage, when possible, a few days prior to seed- 
ing, and it should not come in contact with seeds. 
Two hundred and fifty pounds per acre is a safe dress- 
ing, and when there is sufficient rain to ferment the 
tankage, 400 pounds per acre may be used. A dressing 
of 800 pounds in a dry season would be destructive to 
vegetation. On impoverished soil more may be used 
than on soils which are for various reasons out of 
condition. The cost of the nitrogen, as tankage, may 
be determined from the composition and selling price. 
If tankage containing 7 per cent, of nitrogen and 12 
per cent, of phosphoric acid is selling for $32 per ton, 
what is the cost of the nitrogen per pound ? The 
market value of phosphoric acid, in the form of bones, 
should first be ascertained. Suppose that bone phos- 
phoric acid is selling for 4 cents per pound. The 
phosphoric acid in the ton of tankage would then be 
worth $9.60, making the nitrogen cost $22.40. The 
140 pounds of nitrogen in the ton of fertilizer would 
be worth $22.40, or 16 cents per pound. In eastern 
markets the price of tankage is usually much higher 
than near the large packing houses of the west. 

155, Flesh Meal. — The flesh refuse from slaugh- 



NITROGENODS MANURES I25 

ter-houses is sometimes kept separate from the tank- 
age and sold as flesh meal, the fat and gelatin bein<. 
first removed and used for the manufacture of glue and 
soap. Flesh meal is variable in composition and may 
be very slow m decomposing. It contains from 4 to 
8 per cent, or more of nitrogen with an appreciable 
amount of phosphoric acid. Occasionally it is used 
for feeding poultry and hogs, and cattle to a limited 
extent. When thus used the fertilizer value of the 
dung ,s nearly equivalent to the original value of the 
meal. 

156. Fish Scrap. _ The flesh of fish is very rich in 
nitrogen.^ The offal parts, as heads, fins, tails and in- 
testines, are dried and prepared as a fertilizer. Some 
species of fish which are not edible are caught in large 
numbers to be used for this purpose. In sea-coa!t 
regions fish fertilizer is one of the cheapest and best of 
the nitrogenous manures. It is richer in nitrogen 
than tankage or flesh meal, and in many cases equal 
to dried blood. It readily undergoes nitrification and 
IS a quick-acting fertilizer. 

157- Seed Residues. -Many seeds, as cottonseed 
and flaxseed are exceeding rich in nitrogen. When 
the oil has been removed, the flaxseed and cottonseed 
cake are proportionally richer in nitrogen than the 
original seed. This cake is usually sold as cattle 
food, but occasionally is used as fertilizer. Cotton- 
seed cake contains from 6 to 7 per cent, of nitro- 
gen, and compares fairiy well in nitrogen content with 
animal bodies. Cottonseed cake and meal are not so 
quick-acting as dried blood, but when used in south- 



126 SOILS AND FERTILIZERS 

ern latitudes a little time before seeding, the nitrogen 
becomes available for crop purposes. Oil meals, as 
cottonseed and linseed, containing a high per cent, of 
oil are much slower in decomposing than those which 
contain but little oil. It is better economy to feed the 
cake to stock and use the manure than to apply the 
cake directly to the land. Occasionally however 
cottonseed meal has been so low in price that its use 
as a fertilizer has been admissible. 

A ton of cottonseed meal costing $20 and containing 
2 per cent, of phosphoric acid and 7 per. cent of 
nitrogen would be equivalent to 13.1 cents per pound 
for the nitrogen, which is frequently cheaper than 
purchasing some other nitrogenous fertilizer. 

158. Leather, Wool Waste and Hair are rich in 
nitrogen, but on account of their slow rate of decom- 
posing are unsuitable for fertilizer purposes. When 
present in fertilizers they give poor field results. 

One of the methods employed to detect, in fertili- 
zers, the presence of inert forms of nitrogen as leather, 
is to digest the material in prepared pepsin solution.5° 
Substances like dried blood are nearly all soluble in 
the pepsin, while leather and other inert forms are 
only partially so. The solubility of the organic nitro- 
gen in pepsin solution determines, to a great extent, 
the value of the material as a fertilizer. ^^ 

Soluble in prepared 

pepsin solution 
Per cent, of nitrogen. 

Dried blood 94. 2 

Ground dried fish 75.7 

Tankage 73.6 

Cottons eed meal 86.4 

Hoofand horn rneal 30.0 

Leather 16.7 



NITROGENOUS MANURES 1 27 

159. Peat and Muck. — Many samples of peat and 
muck are quite rich in nitrogen. The nitrogen is, 
however, in an insoluble form, and is with difficulty 
nitrified. When mixed with stable manure, particu- 
larly liquid manure, with the addition of a little lime 
fermentation may be induced, and a valuable manure 
produced. Muck and peat should be dried and sun- 
cured, and then used as absorbents in stables. Peat 
differs from muck in being fibrous. If the muck gives 
an acid reaction, lime (not quicklime) should be used 
with it in the stable, as directed under farm manures. 
When easily obtained muck is one of the cheapest 
forms of nitrogen. 

Composition of Dry Muck Samples.^' 

Nitrogen. 
Per cent. 

Marshy place, producing hay 2.21 

Marshy place, dry in late summer 2.01 

Old lake boUom i .8 r 

160. Leguminous Crops as Nitrogenous Manures. 

^The frequent use of leguminous crops for manurial 
purposes is the cheapest way of obtaining nitrogen. 
When the crop is not removed from the land but is 
plowed under while green, the practice is called green 
manuring. This does not enrich the land with any 
mineral material but results in changing to humate 
forms inert plant food. Green manuring, with le- 
guminous crops, should take the place of bare fallow, 
as its* effects upon the soil are more beneficial. With 
green manuring, nitrogen is added to the soil while 
with bare fallow there is a loss of nitrogen. Legu- 
minous crops, as clover, peas,' crimson clover, and cow 
peas, should be made to serve as the main source of 
the nitrogen for crop production. 



128 SOILS AND FERTILIZERS 

i6i. Sodium Nitrate. — The nitric nitrogen most 
frequently met with in commercial forms is sodium 
nitrate, commonly known as Chili saltpeter. It is a 
natural deposit found extensively in Chili, Peru, and 
the United States of Colombia. Various theories have 
been proposed to account for these deposits, but it is 
difficult to determine just how they have been formed.'° 
Their value to agriculture may be estimated from the 
fact that there are annually used in the United States 
about 100,000 tons, and in Europe about 700,000 tons. 
The commercial value of nitrogen in fertilizers is reg- 
ulated by the price of sodium nitrate which, when 
pure, contains 16.49 P^^ cent, of nitrogen. Commer- 
cial sodium nitrate is from 95 to 97 per cent. pure. 
An ordinary sample contains about 16 per cent, of 
nitrogen and costs from $50 to $60 per ton, making 
the nitrogen worth from 15 to 18 cents per pound. 
Sodium nitrate is the most active of all the nitrogenous 
manures. It is soluble and does not have to undergo 
the nitrification process before being utilized by crops. 
On account of its extreme solubility it should be ap- 
plied sparingly, for it cannot be retained in the soil. 
As a top dressing on grass, it will respond by impart- 
ing a rich green color. It may be used at the rate of 
250 pounds per acre, but a much lighter application 
will generally be found more economical. Sodium 
nitrate may contain traces of sodium perchlorate, 
which is destructive to vegetation if the fertilizer is 
used in excess.s^ Sodium nitrate, in small amounts, 
is the fertilizer most frequently resorted to when the 
forcing of crops is desired as in early market garden- 



NITROGENOUS MANURES 1 29 

ing. Its use for fertilizing horticultural crops has be- 
come equally as extensive as for general farm crops. 
Excessive amounts may produce injurious results. 
Sodium nitrate stimulates a rank growth of dark 
green foliage, and retards the maturity of plants, but 
when properly used is one of the most valuable of 
the nitrogenous fertilizers. 

162. Ammonium Salts. — Ammonium sulphate is 
obtained as a by-product in the manufacture of illumi- 
nating gas and is extensively sold as a fertilizer. It 
usually contains about 20 per cent, of nitrogen, equiv- 
alent to 95 per cent, of ammonium sulphate, the re- 
maining 5 per cent, being moisture and impurities. 
Ammonium sulphate is not generally considered the 
equivalent of sodium nitrate. It is, however, a valua- 
ble form of nitrogen. The statements made regarding 
the use of sodium nitrate apply equally well to the 
useof ammonium sulphate. Ammonium chloride and 
ammonium carbonate are not suitable for fertilizers 
on account of their destructive action upon vegetation. 

163. Nitrogen and Ammonia Equivalent of Fer- 
tilizers. — Nitrogenous fertilizers are sometimes 
represented as containing a certain amount of ammo- 
nia instead of nitrogen. Fourteen-seventeenths of 
ammonia is nitrogen, and if a fertilizer contains 2.25 
per cent, ammonia, it is equivalent to 1.85 per cent, 
of nitrogen. To convert NH results to an N basis 
multiply by 0.823. 

164. Purchasing Nitrogenous Manures. — In pur- 
chasing nitrogenous manure, the special purpose for 
which it is to be used should always be considered. 

■ (9) 



130 SOILS AND FERTILIZERS 

Under some conditions, as forcing a crop on an im- 
poverished soil, sodium nitrate is desirable. Under 
other conditions tankage, cottonseed cake, or some 
other form of nitrogen may be made to answer the 
purpose. There is annually expended in purchasing 
nitrogenous fertilizers a large amount of money which 
could be expended more ecomically, if the science of 
fertilizing were given a more careful study. The 
uses of nitrogenous fertilizers for special crops and 
the testing of soils to determine any deficiency in 
nitrogen are discussed in Chapters X and XI which 
treat of commercial fertilizers and the food require 
ments of farm crops. 



CHAPTER V 

FARM MANURE 

165. Variable Composition of Farm Manures. — 

The term farm manure does not designate a prod- 
uct of definite composition. Manure is the most 
variable in chemical composition of any of the mate- 
rials produced on the farm. It may contain a large 
amount of straw, in which case it is called coarse ma- 
nure ; or it may contain only tl;p solid excrements and 
a little straw, the liquid excrements being lost by 
leaching ; then again it may consist of the droppings 
of poorly fed animals, or of the mixed excrements of 
different classes of well-fed animals. 

The term stable manure has been proposed for 
that product which contains all of the solid and liquid 
excrements with the necessary absorbent, before any 
losses have been sustained.'^ The term barnyard 
manure is restricted to that material which accumu- 
lates around some barns and farm yards, and is ex- 
posed to leaching rains and the drying action of the 
sun. 

166. Average Composition of Manures. — The solid 
excrements of animals contain from 60 to 85 per cent, 
of water ; when mixed with straw, and the liquid ex- 
crements are retained, the mixed manure contains 
about 75 per cent, of water. The nitrogen varies 
from 0.4 to 0.9 per cent., according to the nature of 
the food and the extent to which other factors have 



132 



SOILS AND FERTILIZERS 



affected the composition. In general, animals consu- 
ming liberal amounts of coarse fodders produce manure 




^. 2. Ira 

Fig. 24. Average composition of 

fresh manure. 
I. Nitrogen. 2. Phosphoric acid. 
3. Potash. 4. Mineral matter. 




Fig. 25. Manure after six 
months' exposure. 



with a higher per cent, of potash than of phosphoric 
acid. This is because the potash in the food exceeds 
the phosphoric acid. The average composition of 
mixed stable manure is as follows : 



Average 
Per cent. 



Nitrogen 0.50 

Phosphoric acid 0.35 

Potash 0.50 



Range 
Per cent. 

0.4 to 0.8 

0.2 to 0.5 

0.3 to 0.9 



In calculating the amount of fertility in manures, 
it is more satisfactory to compute the value from the 
food consumed and the care which the manure has 
received, than to use figures expressing average com- 
position. 

167. Factors which Influence the Composition and 
Value of Farm Manure. — 

I. Kind and amount of absorbents used. 

II. Kind and amount of food consumed. 



FARM MANURE 1 33 

III. Age and kind of animals. 

IV. Methods employed in collecting-, preserving 
and utilizing the manure. 

Any one of the above, as well as many minor 
factors, may influence the composition and value of 
farm manure. 

168. Absorbents. — The most universal absorbent 
is straw. Wheat straw and barley straw have about 
the same manurial value. Oat straw is more valu- 
able. The average composition of straw and other 
absorbents is as follows : 

straw. I^eaves. Peat. Sawdust. 

Per cent. Per cent. Per cent. Per cent. 

Nitrogen 0.40 0.6 i.o o.i 

Phosphoric acid 0.36 0.3 .. 0.2 

Potash 080 0.3 .. 0.4 

When a large amount of straw is used the per cent. 
of nitrogen and phosphoric acid is decreased, while the 
per cent, of potash is slightly increased. Sawdust 
and leaves both make the manure more dilute. Dry 
peat makes the manure richer in nitrogen. The ' ab- 
sorbent powers of these different materials are about 
as follows : ^'^ 

Per cent, of 
water absorbed. 

Fine cut straw 30.0 

Coarse uncut straw 18.0 

Peat 60.0 

Sawdust 45.0 

The proportion of absorbents in manure ranges from 
a fifth to a third of the total weight of the manure. 

169. Use of Peat and Muck as Absorbents. — On 
account of the high per cent, of nitrogen in peat and 



134 SOII,S AND FERTII.IZKRS 

the power which it possesses when dry of absorbing 
water, it is a valuable material to nse as an absorbent 
in stables. As previously explained, peat is slow of 
decomposition, but when mixed with the liquid ma- 
nure it readily yields to fermentation, particularly if 
a little land plaster or marl be used in the stable along 
with the peat. Peat has high absorptive power for 
gases as well as liquids, and when used stables are 
rendered particularly free from foul odors. 

RELATION OF FOOD CONSUMED TO MANURE PRODUCED 

170. Bulky and Concentrated Foods. — The more 
concentrated and digestible the food consumed, the 
more valuable is the manure. Coarse bulky fodders 
always give a large amount of a poor quality of ma- 
nure. For example, the manure from animals fed on 
timothy hay and that from animals fed on clover hay 
and grain, show a wide difference in composition. 
The dry matter of timothy hay is about 55 per cent, 
digestible. From a ton of timothy hay there will be 
about 790 pounds of dry matter in the manure. The 
nitrogen, phosphoric acid, and potash in the food con_ 
sumed are nearly all returned in the manure, except 
under those conditions which will be noted. The 
manure from a ton of mixed feed, as clover and bran, 
is smaller in amount but more concentrated than that 
produced from timothy. In a ton of timothy and 
in a ton of mixed feed (1500 lbs. clover, 500 lbs. bran) 
there are present : 

Timothy. Mixed feed. 

I,bs. " lybs. 

Nitrogen 25.0 40.0 

Phosphoric acid 9.0 24.0 

Potash 40.0 30.0 



FARM MANURE 1 35 

The nitrogen, phosphoric acid, and potash in these 
two rations are retained in the animal body in dis- 
similar amounts ; lo per cent, more of these elements 
being retained from the more liberal ration, due to 
more favorable conditions for growth. Making al- 
lowance for this fact there will be present in the ma- 
nure from the mixed feed one-half more nitrog-en, and 
two and one-half times as much phosphoric acid, as 
in the manure from the timothy hay, which, free 
from bedding, contains about 790 pounds of indigesti- 
ble matter while the manure from the mixed feed con- 
tains 760 pounds, the mixed ration being more digesti- 
ble. If both manures contain the same amount of ab- 
sorbents, the manure from the ton of mixed clover 
and bran will weigh slightly less, but contain more 
fertility than that from the timothy hay. 

The value of manure can be accurately determined 
from the composition of the food consumed and 
the care which the manure has received. Only a 
small amount of the nitrogen in the food is retained 
in the body. The larger portion is used for repair 
purposes. The nitrogen of the tissues which have 
been renewed is voided as urea in the liquid excre- 
ments. Some of the nitrogenous compounds of the 
food are utilized for the production of fat, in which 
case the nitrogen is voided in the excrements. The- 
fact that but little of the nitrogen and mineral matter 
of the food, under most conditions, is retained in the 
body may be observed from the figures of Lawes and 
Gilbert relating to the composition of the flesh added 
to animals while undergoing the fattening process.^s 



136 SOILS AND FERTILIZERS 

Increase during Fattening. 

Dry Nitrogenous 

Water. matter. Fat. matter. Ash. 

Ox . 24.6 75.4 66,2 7.69 1.47 

Sheep 20.1 79.9 70.4 7.13 2.36 

Pig 22.0 78.0 71.5 6.44 0.06 

The results of numerous digestion experiments 
show that when the food undergoes digestion from 5 
to 15 per cent, of the nitrogen is, as a rule, retained 
in the body. The nitrogen of the food is utilized 
largely to replace that which has been required for 
vital functions. The nitrogen of the food enters the 
body, undergoes digestion changes, is utilized for 
some vital function, and is then voided in the excre- 
ments. 

The digestion of food has been compared to the 
combustion of fuel : the undigested products of the 
solid excrements represent the ashes, and the urine 
represents the volatile products. When wood is burn- 
ed the nitrogen is converted into volatile . products. 
When food is digested and utilized by the body the 
digestible nitrogen is mainly converted into urea, 
while the indigestible nitrogen is voided in the dung. 
In the solid and liquid excrements of animals, from 
80 to 95 per cent, of the nitrogen, phosphoric acid 
and potash of the food are present. 

171. Composition of Solid and Liquid Excrements 
Compared. — In composition the liquid excrements 
differ from the solids in having a much larger amount 
of nitrogen and less phosphoric acid.^^ 



FARM MANURE I 37 

Water. Nitrogen. Phosphoric acid. Potash. 

Solids. Liquids. Solids. Liquids. Solids. Liquids. Solids. 

Percent. Percent. Percent. Percent. Percent. Percent. Percent 

Cows.. 76 89 0.50 1,20 0.35 ... 0.30 

Horses 84 92 0.30 0.86 0.25 ... o.io 

Pigs... 80 97.0 0,60 0.80 0.45 0.12 0.50 

Sheep. 58 86.5 0.75 1.40 0.6) 0.05 0.30 

The nitrogen in the food consumed influences the 
amount of water in the manure. As a rule, a highly 
concentrated nitrogenous ration, produces a higher per 
cent, of water in the manure than a well-balanced 
ration. There is but little phosphoric acid in the 
liquid excrements of horses and cows, while the urine 
of sheep and swine contains appreciable amounts of 
this element. 

The liquid manure is more constant both in compo- 
sition and amount than the solid excrements. This 
fact may be observed from the following table, which 
gives the composition of the solid and liquid excre- 
ments from hogs when fed on different amounts of 
grain. 57 







Solid 


excrements. 


Liquid excrements. 






s 
<l>4 


IS 


1 

Phosphoric 

acid. 
Per cent. 


] 
Nitrogen 
Per cent. 


Phosphoric 
acid. 
Per cent. 


Lbs 


. Kind of food daily. 












9f 


Barley and shorts 


8 


0.57 


0.72 


2.05 


0,06 


6 


Barley 


4 


0.43 


0.70 


2.06 


0.16 


5i 


Corn and shorts. 


2^ 


0.80 


.... 


2.65 


0,20 


6i 


Corn 


It 


0.82 


0.89 


2.05 


0.29 



(In each experiment the amount of liquid excrements was four pounds.) 



138 SOII.S AND FERTII.IZKRS 

The amount of nitrogenous waste matter in the 
urine is nearly the same whether an animal be gaining 
or losing in flesh, consequently the urine is more con- 
stant in both composition and quantity than the solid 
excrements. 

The amount and composition of the solid excre- 
ments vary with the amount and kind of food con- 
sumed. If the food is indigestible the solid excrements 
contain a larger part of the nitrogen as indigestible 
protein. When an animal is properly supplied with, 
food for all purposes, normal conditions exist, and the 
amount of nitrogen voided in the liquid and solid ex- 
crements is equal to that supplied in the food con- 
sumed, except in the case of growing and milk pro- 
ducing animals. 

Experiments at the Rothamsted station have shown 
that from 57 to 79 per cent, of the total nitrogen in 
the food of farm animals is voided in the liquid ex- 
crements, and from 16 to 22 per cent, is voided in the 
solid excrements. Nearly all of the mineral elements 
in the food is voided in the excrements, less than four 
per cent, being retained in the body ; in the case of 
milk cows about 10 per cent, of the ash in the food 
is recovered in the milk. 

172. Manural Value of Foods. — The manurial 
value of a fodder is determined by the amount of nitro- 
gen, phosphoric acid, and potash present in the 
material. Timothy hay, for example, has a manurial 
value of $5.30 per ton, which means that if the nitro- 



FARM MANURE I39 

gen, phosphoric acid, and potash in the timothy hay 
were purchased in commercial forms they would cost 
$5.30. Lawes and Gilbert estimate that 80 per cent, 
of the fertility in fodders is, as a rule, returned in the 
manure. 

In the following table are given the pounds of 
nitrogen, phosphoric acid, and potash per ton of 
some food materials :" 

Nitrogen. Phosphoric acid. Potash. 

Lbs. Lbs. Lbs. 

Timothy hay 25 9 40 

Clover hay 35 14 30 

Wheat straw 11 4 12 

Oat straw 12 4 18 

Wheat 45 20 12 

Oats 33 16 II 

Barley 40 18 11 

Rye 42 20 13 

Flax 87 32 14 

Corn 32 T4 8 

Wheat shorts 48 31 20 

Wheat bran 54 52 30 

Ivinseed meal 100 35 25 

Cottonseed meal 130 35 56 

Milk 10 3 3 

Cheese 90 23 5 

Live cattle 53 37 3 

Potatoes 7 3 II 

Butter I I J 

Ivive pigs 40 17 3 

17a. Commercial Value of Manures. — When the 
value of farm manure is calculated on the same basis 
with commercial fertilizers it will be found that 
stable manure is worth from $2 to I3.50 per ton. The 
value of the increased crops resulting from its use 



I40 SOILS AND FERTILIZERS 

varies with conditions. Farm manures favorably in- 
fluence the yield of crops for a number • of years. 
After a dressing of 8 tons of farm manure, average 
prairie land will yield 20 bushels per acre more corn 
the first year, 5 bushels more wheat the second year, 
and 8 bushels more of other grains the third year, 
with slightly increased yields in subsequent years. 
It takes about three years for the manure to entirely 
repay the cost of its application. Its influence is felt 
however for a much longer time. It is sometimes 
stated that the phosphoric acid and potash in stable 
manure is not as soluble as that in commercial 
fertilizers, and consequently is worth less. While 
not so soluble in the form of manure, it frequently 
happens that the phosphoric acid and potash in 
the commercial fertilizers become, through flxation 
processes, less soluble when mixed with the soil than 
the same elements in stable manure. 

Stable manure is valuable not only for the fertility 
contained but also because it makes the inert plant 
food of the soil more available and exercises such a 
favorable influence on the water supply of crops ; 
hence it is justifiable to assign the same value to the 
elements in well-prepared farm manures as to those in 
commercial fertilizers. 

If well-prepared stable manure is not worth $2.50 
per ton, then too much, accordingly, is paid for com- 
mercial forms of plant food. 

INFLUENCE OF AGE AND KIND OF ANIMAL 

174. Manure from Young and Mature Animals. — 



AGE AND KIND OF STOCK I4I 

The manure from older animals is somewhat more 
valuable than that from young animals, even when 
fed the same kind of food. This is because more of 
the phosphoric acid and nitrogenous matters are re- 
tained in the body of a young animal. It is not so 
much a difference in digestive power as a difference 
in retentive power. In older animals the proportion 
of new nitrogenous tissue produced is much less than 
in young animals, and more of the nitrogen of the food 
is used for repair purposes and subsequently voided in 
the manure, while with younger animals more of the 
nitrogen of the food is retained for the construction 
of new muscular tissue. 

When an animal is neither gaining nor losing in 
flesh, and is not producing milk, an equilibrium is es- 
tablished between the nitrogen in the food supply and 
the nitrogen in the manure. Under such conditions 
practically all of the nitrogen of the food is returned 
in the manure.57 

175. Cow Manure. — A milch cow when fed a bal- 
anced ration, will make from 60 to 70 pounds of solid 
and liquid manure a day, of which 20 to 30 pounds 
are liquid excrements. The solid excrements contain 
about 6 pounds of dry matter. When a cow is fed 
clover hay, corn fodder, and grain, about half of the 
nitrogen of the food is in the urine, about one-fourth 
in the milk, and the remainder in the solid excre- 
ments. Hence, if the solid excrements only are col- 
lected but a quarter of the nitrogen of the food is ob- 
tained, while if both solids and liquids are utilized 



142 SOILS AND FERTILIZERS 

three-quarters of the nitrogen is secured. Cow manure 
is extremely variable in composition, and is the most 
bulky of any manure produced by domestic animals. 
A well-fed cow will produce about 80 lbs. of manure 
per day, including absorbents. 

176. Horse Manure. — Horse manure contains less 
water than cow manure, and is of a more fibrous 
nature, doubtless due to the horse possessing less 
power for digesting cellulose materials. Horse ma- 
nure readily ferments and gives off ammonia products. 
When the manure becomes dry, fire-fanging results, 
due to rapid fermentation followed by the growth of 
fungus bodies. Horse manure is sometimes consider- 
ed of but little value. This is because it so readily 
deteriorates in value and when used it has lost 
much of its nitrogen by fermentation. When mixed 
with cow manure, both manures are improved, 
the rapid fermentaion of the horse manure is checked, 
and at the same time the cow manure is improved in 
texture. It is estimated that horses void about three- 
fifths of their manure in the stable. A well-fed horse 
at ordinarily hard work will produce about 50 pounds 
of manure per day, of which about one-fourth is urine. 
A horse will produce about 6 tons of manure per year 
in the stable. If properly preserved and used it is a 
valuable, quick-acting manure, but if allowed to fer- 
ment and leach it gives poor results. 

177. Sheep Manure. — Sheep produce a small 
amount of concentrated manure, containing less water 
than that produced by any other domestic animal. It 



AGE AND KIND OF STOCK 143 

readily ferments and is a quick-acting fertilizer. 
When mixed with horse and cow manure the mixture 
ferments more evenly. Because of the small amount 
of w^ater, sheep manure is very concentrated in composi- 
tion. It is valuable for general gardening purposes, or 
whenever a concentrated quick acting manure is desired. 

178. Hog Manure. — Hog manure is not constant 
in composition on account of the varied character of the 
food consumed. The manure from fattening hogs 
which are well fed compares favorably in composition 
and value with the manure produced by other ani- 
mals. It contains a high per cent, of water, and, like 
cow manure, may be slow in decomposing. On ac- 
count of containing so much water, losses by leach- 
ing readily occur. From a given weight of grain, 
pigs produce less dry matter in the manure than 
sheep or cows. The liquid excrements of well-fed 
hogs are rich in nitrogen, containing, on an average, 
about 2 per cent. The solid excrements when leached, 
fermented and deprived of the liquid excrements have 
but little value as fertilizer. 

179, Hen Manure. — Like all other farm manures 
hen manure is variable in composition. The nitrogen 
is present mainly in the form of ammonium com- 
pounds. This makes it a quick-acting fertilizer. 
When fowls are well-fed the manure contains about 
the same amount of nitrogen as sheep manure. Hen 
manure readily ferments, and if not properly cared 
for losses of nitrogen, as ammonia, occur. It is not 
advisable to mix hard wood ashes or ordinary lime 



144 SOIIvS AND FERTILIZERS 

with hen manure because the ammonia is so readily 
liberated by alkaline compounds. The value of hen 
manure is due to its being a quick-acting fertilizer 
rather than to its containing such a large amount of 
fertility. A hen produces about a bushel of manure 
per year. 5^ 

Composition of Hen Manure. 

Per cent. 
Water 57-50 

Nitrogen 1.27 

Phosphoric acid 0.82 

Potash. 0.28 

180. Mixing of Solid and Liquid Excrements. — 

The solid and liquid excrements, when properly mixed, 
make a well-balanced manure. The urine alone is 
not a complete manure, as it is deficient in phosphoric 
acid and other mineral matter. The solid excrements 
with the urine, when mixed with soil, readily undergo 
nitrification. The nitrogen in the solid excrements 
is in the form of indigestible protein, and is rendered 
available as plant food more slowly. Land heavily 
dressed with leached manure has received an unbal- 
anced fertilizer deficient in nitrogen but fairly well 
supplied with mineral matter. A soil thus manured 
may fail to respond because of the unbalanced char- 
acter of the manure. 

181. Volatile Products from Manure. — Fermen- 
tation of manure in stables results in the production 
of a large number of volatile compounds and in loss 
of manurial value. Urea, when it ferments, produces 
ammonia, which combines with the carbon dioxide 
always present in stables in liberal amounts as a pro- 



AGE AND KIND OF STOCK I45 

duct of respiration, and forms ammonium carbonate, 
a volatile compound. When the stable atmosphere 
becomes charged with ammonium carbonate some of 
it is deposited on the walls of the stable, forming a 
white coating. The white coating found on harnesses 
and carriages stored in poorly ventilated stables, is 
ammonium carbonate. Accumulations of manure in 
the stable and poor ventilation are the conditions fav- 
orable to the production of this compound. 

182. Human Excrements. — The use of human ex- 
crements as manure is sometimes advised, and in some 
countries they are extensively used. When fresh, 
they may contain a high per cent, of nitrogen and 
phosphoric acid ; when fermented, a loss of nitrogen 
has occurred. Heiden estimates that in a year i,ooo 
pounds of excrements per person are made, which 
contain $2.25 worth of fertility.59 For sanitary rea- 
sons, human excrements should be used with great care. 
It is doubtful with the abundance and cheapness of 
plant food whether their extensive use as manure is 
advisable. About 1840, Leibig expressed the fear that 
the essential elements of plant food would accumulate 
in the vicinity of large cities and be wasted, and that 
in time there would be a decline in fertility due to 
this cause. ^° Many political economists shared the 
same fear. Since that time the fixation of atmos- 
pheric nitrogen through the agency of leguminous 
crops has been discovered, extensive beds of sodium 
nitrate, phosphate rock and Stasfurt salts, have been 
utilized and larger areas of more fertile soils have been 

(10) 



146 SOII.S AND FERTILIZERS 

brought under cultivation, so that it is not now so 
essential to devise means for utilizing human excre- 
ments as manure. 

THE PRESERVATION OF MANURE 

183. Leaching. — Leaching of manure is the greatest 
source of loss. Experiments by Roberts have shown 
that when horse manure is thrown in a loose pile and 
subjected to the joint action of leaching and weather- 
ing it may lose in six months nearly 60 per cent, of 
its most valuable fertilizing constituents. The tab- 
ular results are as follows : '^ 

April 25. Sept. 28. Loss. 

Lbs. Lbs. Per cent. 

Gross weight 4,000 i, 730 57 

Nitrogen 19.60 7.79 60 

Phosphoric acid .. . 14.80 7.79 47 

Potash 36.0 8.65 76 

Value per ton $2.80 $1 .06 

Cow manure, on account of its more compact nature, 
does not leach so readily as horse manure. A similar 
experiment with cow manure, conducted at the same 
time, showed the following losses : 

April 25. Sept 28. Loss. 

Lbs. Lbs. Pef cent. 

Gross weight 10,000 5*125 49 

Nitrogen 47 28 4-1 

Phosphoric acid • • 32 26 19 

Potash 48 44 8 

Value per ton |2 . 29 $1 .60 

When mixed cow and horse manure was compacted^ 
and " placed in a galvanized iron pan with a perfo- 
rated bottom " for six months, the losses were as fol- 
lows : 



THK PRESERVATION OF MANURE 147 

March 29. Sept. 30. Loss, 

lybs. I,bs. Per cent. 

Gross weight 226 222 

Nitrogen 1.04 i.oi 3.2 

Phosphoric acid • . 0.61 0.58 4.7 

Potash 1.20 0.43 35.0 

Value per ton I2.38 $2,16 

184. Losses by Fermentation. — When rapid fer- 
mentation takes place in manure, appreciable losses of 
nitrogen may occur. When the manure is well com- 
pacted and the pile is so constructed as to prevent the 
rapid circulation of air through it, losses are reduced 
to the minimum. Experiments have shown that 
when leaching is prevented, the loss of nitrogen by 
fermentation of the mixed manure is very small. 
Under poor conditions losses by fermentation may 
exceed 15 per cent. Hen manure, sheep man- 
ure and horse manure suffer the greatest losses by 
rapid fermentation. When extreme conditions, as ex- 
cessive moisture, drought and high temperature, fol- 
low each other, then the greatest losses occur. 

185. Different Kinds of Fermentation. — The large 
number of organisms present in manure all belong to 
one of two classes : (i) aerobic, or (2) anaerobic. The 
aerobic ferments require an abundant supply of 
air in order to carry on their work. When deprived 
of oxygen they become inactive. The anaerobic fer- 
ments require the opposite condition. They become 
inactive in the presence of oxygen and can thrive only 
when air is excluded. In the center of a well-con- 
structed manure pile anaerobic fermentation takes 
place while on the surface aerobic fermentation is act- 



148 SOILS AND FERTILIZERS 

ive. The anaerobic ferments prepare the way for the 
action of the aerobic bodies. When aerobic fermenta- 
tion is completed the organic matter is converted into 
water, carbon dioxide, ammonia and allied gases. 
From what has been said regarding the action of these 
two classes of ferments it is evident that anaerobic 
fermentation is the most desirable. 




Fig. 26. Fermentation of Manure. 

186. Water Necessary for Fermentation. — In order 
to produce the best results in fermenting manure, 
water is necessary. If the manure becomes too dry 
abnormal fermentation takes place. Water is always 
beneficial on manure so long as leaching is prevented; 
for it encourages anaerobic fermentation by excluding 
the air. An excessive amount of water, such as falls 
on piles from the eaves of buildings, is more than is 
required for good fermentation. During a dry time it 
is beneficial, if conditions admit, to water the com- 
post pile. 

187. Heat Produced During Fermentation. — Dur- 
ing active fermentation of horse and sheep manure, a 
temperature of 175° F. may be reached by the fer- 
menting mass. Ordinarily, however, the temperature 



THE PRESERVATION OF MANURE 149 

of the manure pile ranges from iio° to 130° F. The 
highest temperature is near the surface where fermen- 
tation is most rapid. The temperature of fermenta- 
tion may be sufficiently high, if the manure is mixed 
with litter, to cause spontaneous combustion. 

188. Composting Manure May Improve Its Quality; 
— Composting manure so that leaching and rapid fer- 
mentation do not take place may improve its quality, 
making it more concentrated. Pound for pound, 
composted manure is more concentrated than fresh 
manure, because, if properly cared for, nearly all of 
the nitrogen, phosphoric acid, and potash of the orig- 
inal manure are obtained in a smaller bulk. A ton 
of composted manure is obtained from about 2,800 
pounds of stable manure. Composting is sometimes 
resorted to in order to destroy obnoxious weed seeds. 

Fresh Composted 
manure. manure. 

Per cent. Per cent. 

Nitrogen 0,50 0.60 

Phosphoric acid 0.28 0.39 

Potash • 0.60 0.80 

In composting manure it should be the aim to in- 
duce anaerobic fermentation by excluding the air and 
retaining the water. This can be accomplished best 
by using mixed manure and making a compact pile, 
capable of shedding water. The compost pile should 
be shaded to secure better conditions for fermentation. 
If the'pile becomes offensive a little earth on the sur- 
face will absorb the odors. 

189. Use of Preservatives. — The use of preserva- 
tives, as gypsum and kainit, has been recommended 



I50 SOILS AND FERTILIZERS 

to prevent fermentation losses. Opinions differ as to 
their value. Moist gypsum, when it comes in contact 
with ammonium carbonate, produces ammonium sul- 
phate, a non-volatile compound, 

(NH XCO3 + CaSO = (NH XSO^ + CaCO^. 

Gypsum is used at the rate of about one-half pound 
per day for each animal. ^9 Experiments have shown 
that it may prevent a loss of 5 per cent, of the nitro- 
gen of horse manure. It may be safely sprinkled in 
the stalls as it has no action on the feet of animals. 
When it is necessary to use gypsum as a fertilizer it 
is advantageous to use it in stables. It is not advisable 
to use lime in any other form than the sulphate. Un- 
slaked lime will decompose manure and liberate am- 
monia. Neither kainit nor gypsum should be used 
when manure is exposed to the leaching action of 
rains. Preservatives cannot be made to take the place 
of care in handling manure ; they should be used only 
when the manure receives the best of care. 

190. Manure Produced in Sheds and BoxS tails. — 

Manure produced under cover as in sheds and box 
stalls is of superior quality to that prepared in 
any other way. Losses by leaching are avoided, 
the manure is compacted by the tramping of the 
animals, the solid and liquid excrements are more 
evenly mixed with the absorbents, and the conditions 
are favorable for anearobic fermentation. By no other 
system is there such a large percentage of the fertility 
recovered. Manure from w^ell-fed cattle, when col- 



THK USE OF MANURE I5I 

lected and prepared in a shed, will have about the 
following composition : 

Per cent. 

Water 70.00 

Nitrogen 0.90 

Phosphoric acid 0.60 

Potash o. 70 

191. Value of Protected Manure. —Manure that 
is produced under cover has greater crop-producing 
power than when cared for in any other way. Ex- 
periments by Kinnard show that such manure pro- 
duced 4 tons more potatoes per acre than pile manure, 
while 1 1 bushels more wheat per acre were obtained 
from land which had the previous year received the 
covered manure than from land which received the 
uncovered manure.^^ 

THE USE OF MANURE 

192. Direct Hauling to Fields.— It is always desir- 
able, whenever conditions allow, to draw the manure 
directly to the field and spread it, rather than to allow 
it to accumulate about barns or in the barnyard. 
When taken directly to the field from the stable no 
losses by leaching occur, and the slight loss from fer- 
mentation and volatilization of the ammonia are more 
than offset by the benefits derived from the action of 
the fresh manure upon the soil. When manure un- 
dergoes fermentation in the soil, as previously stated, 
it combines with the mineral matter of the soil and 
produces humates. The practice of hauling the ma- 
nure directly to the field and spreading it with a ma- 
nure spreader is the most economical way of caring 
for it. 



152 SOILS AND FERTILIZERS 

With scant rainfall, composting the manure before 
spreading is necessary, but with liberal rainfall it is 
not essential. On a loam soil a direct application of 
stable manure is more advisable than on heavy clay 
or light sandy soils. In the case of sandy soils there 
is frequently an insufficient supply of water to prop- 
erly ferment the manure. Manure sometimes fails to 
show any beneficial effects the first year on heavy clay 
land, because of the slow rate of decomposition, but 
the beneficial effects are noticeable the second and 
third years. 

193. Coarse Manure May Be Injurious.— The ap- 
plication of coarse leached manure may cause the soil 
to be so open and porous as to affect the water supply 
of the crop, by introducing, below the surface soil, a 
layer of straw, which breaks the capillary connection 
with the subsoil. Coarse manure and shallow spring 
plowing are sometimes injurious, where fine or well- 
composted manure and fall plowing are beneficial. 
The trouble resulting from the use of coarse manure 
may be due to its being allowed to leach before it is 
used, so that it does not readily ferment in the soil. 

194. Manuring Pasture Land. — In regions where 
manure decomposes slowly, it is sometimes advisable 
to spread it upon pasture land as a top dressing. The 
manure encourages the growth of grass, so that it ap- 
propriates plant food otherwise lost ; it also acts as a 
mulch preventing excessive evaporation. Then when 
the pasture land is plowed and prepared for a grain 
crop it contains a better store of both water and avail- 



THE USE OF MANURE 



53 



able plant food. The manuring of pasture lands is 
one of the best ways of utilizing the manure when 
trouble arises from slow decomposition. 





Fig. 27. Manured land. 

•:-i!!i^';;ii,'ii!SiMiiiEiW!i!ii:;i'!iiit'tii;hiii'^ 



i 



Fig. 28. Unmanured land. 

195. Small Manure Piles Undesirable. — It is 

sometimes the custom to make a large number of 
small manure piles in fields. This is a poor practice, 
for it entails additional expense in spreading the ma- 
nure, and the small piles are usually so constructed 
that heavy losses occur, and the manure, when finally 
spread, is not uniform in composition. Oats grown 
on land manured in this way present an uneven ap- 
pearance. There are small patches of thrifty, overfed 
oats, corresponding to the places occupied by the 
former manure piles, while large areas of half-starved 
oats may be observed. 



154 SOILS AND FERTILIZERS 

196. Rate of Application. — The amount of manure 
that should be applied depends upon the nature of the 
soil and the crop. On loam soils intended for general 
truck purposes heavier applications may be made than 
when grain is raised. For general farm purposes, 6 
to 8 tons per acre are usually sufficient. It is better 
economy to make frequent light applications than 
heavier ones at long intervals. When manure is 
used frequently the soil is kept in a more even state 
of fertility, and losses by percolation, denitrification, 
and ammonification are prevented. Too often the 
manure is not evenly distributed about the farm, fields 
adjacent to stables are heavily manured, while those 
at a distance receive none. 

For growing garden crops 20 tons and more per 
acre are sometimes used. It is better, however, not 
to use stable manure in excess for trucking, but to 
supplement it with special fertilizers as the crops may 
require. Soils which contain a large amount of cal- 
cium carbonate will not become acid when farm ma- 
nure is used, and hence admit of more frequent and 
heavier applications than soils which are deficient in 
this compound. The lime aids fermentation and ni- 
trification. 

197. Crops Most Suitable for Manuring. — Soils 
which contain a low stock of fertility admit of manur- 
ing for the production of almost any crop. Soils well 
stocked with plant food, like some of the western 
prairie soils, which are in need of manure mainly for 
its physical action, will not admit of its direct use on 



THE USE OF MANURE I55 

all crops. On a prairie soil of average fertility an 
application of well-rotted manure may cause wheat to 
lodge. When manure cannot be applied directly to 
a crop, it may be used indirectly. It never injures 
corn by causing too rank a growth, and when wheat 
follows corn which has been manured there is but 
little danger of loss from lodging. 

On some soils stable manure cannot be used for 
growing sugar-beets ; on other soils it does not seem to 
exercise an injurious effect. Tobacco is injured as to 
quality by manure. Crops, as flax, tobacco, sugar- 
beets and wheat, which do not admit of direct appli- 
cations of stable manure all require the manuring of 
preceding crops. When in doubt as to what crop to 
apply the manure to, it is always safe to apply it to 
corn, and then to follow with the crop which would 
have been injured by its direct application. 

The facts that coarse, leached manure may cause 
trouble in a dry season, and that well-rotted manure 
may cause grain to lodge, are no substantial reasons 
why manure should be wasted as it frequently is in 
western farming by being burned, used for making 
roads, thrown away in streams, or used for filling up 
low places. 

198. Comparative Value of Forage and Manure. — 

The manure from a given amount of grain or fodder 
always gives better results than the food itself used 
directly as manure. The manure from a ton of bran 
will give better returns than if the bran itself 
were used. This is because so little of the fertility 



156 SOILS AND FERTILIZERS 

is lost during the process of digestion, and the 
action of the digestive fluids upon the food makes the 
manure more readily available as a fertilizer than the 
food which has not passed through any fermentation 
stages. It is better ecomony to use products as lin- 
seed meal and cottonseed meal for feeding stock, and 
to take good care of the manure, than to use the mate- 
rials directly as fertilizer. 

199. Lasting Effects of Manure. — No other ma- 
nures make themselves felt for so long a time as farm 
manures. In ordinary farm practice an application of 
stable manure will visably affect the crops for a num- 
ber of years. At the Rothamsted Experiment Station, 
records have been kept for over fifty years as to the 
effects of manures upon soils. In one experiment 
farm manure was used for twenty years and then dis- 
continued for the same period. It was observed that 
when its use was discontinued there was a gradual de- 
cline in crop-producing power, but not so rapid as on 
plots where no manure had been used. The manure 
which had been applied for the twenty-year period 
made itself felt for an ensuing period of twenty years. 

200. Comparative Value of Manure Produced on 
Two Farms. — The fact that there is a great differ- 
ence in the composition and value of manures pro- 
duced on different farms may be observed from the 
following examples : 

On one farm 10 tons of timothy are fed. The 
liquid manure is not preserved and 25 per cent, 
of the fertility is leached out of the solid excre- 



THE USE OF MANURE 



157 



ments, while 5 per cent, of the nitrogen is lost by 
volatilization. It is estimated that half of the nitro- 
gen and potash of the food is voided in the urine. 
On account of the scant amount and poor quality of 
the food no milk or flesh is produced. 

On another farm 7.5 tons of clover hay and 2.5 tons 
of bran are fed. The liquid excrements are collected 




Fig. 29. Good manure. 



Fig. 30. Poor manure. 



I. Nitrogen. 
3. Potash. 



2. Phosphoric acid. 
4. Mineral matter. 



and the manure is taken directly to the field and 
spread. It is estimated that 20 per cent, of the nitro- 
gen and 4 per cent of the phosphoric acid and potash 
are utilized for the production of flesh and milk. 

The comparative value of the manures from the 
two farms is as follows : 



Farm No. i. 



In 10 tons timothy, 
Lbs. 



Nitrogen 250 

Phosphoric acid 90 

Potash 400 



Loss in urine. 



250- 
400 



125 lbs. nitrogen 
200 lbs. potash 



158 SOILS AND FERTILIZERS *■ 

Farm No. i. — {Contimied). 

I^oss by I,eaching. 
125 X 0-30 = 37.50 lbs. nitrogen 
90 X 0.25 =• 22.50 lbs. phosphoric acid 
200 X 0-25 = 50 lbs. potash 

Total loss, 
lybs. Per cent. 

Nitrogen 162.5 • 65 

Phosphoric acid 22.5 25 

Potash 250.0 62 

Present in final product, 
manure from i ton timothy. 
I,bs. 

Nitrogen 8.75 

Phosphoric acid 6.75 

Potash 15.00 

Relative money value |i.oo 

Farm No. 2. 

In 10 tons mixed feed. 
I.bs. 

Nitrogen 400 

Phosphoric acid • 240 

Potash 300 

I^oss, sold in milk and retained in body. 
Lbs. Per cent. 

Nitrogen 400 X o-2o 80 20 

Phosphoric acid, estimated. . . 10 4 

Potash 12 4 

Present in final product, 

manure from i ton feed. 

Lbs. 

Nitrogen 32.0 

Phosphoric acid 23.0 

Potash 26.0 

Relative money value $3-80 

201. Summary of Ways in which Stable Manure 
May Be Beneficial. — Farm manures act upon soils 
both chemically and physically : 
{a) Chemically : 

I. By adding new stores of plant food to the soil. 



THE VALUK OF MANURE 1 59 

2. By acting upon the soil, forming humates and 
rendering the inert mineral plant food of the soil more 
available. 

3. By raising the temperature of the soil, as the re- 
sult of chemical action. 

[b) Physically : 

4. By making the soil darker colored. 

5. By enabling soils to retain more water and to 
give it up gradually to growing crops. 

6. By improving the physical condition of sandy 
and clay soils. 

7. By preventing the denuding effects of heavy 
wind storms. 



CHAPTER VL 



FIXATION. 

202. Fixation, a Chemical Change. — When a fer- 
tilizer is applied to a soil, chemical reaction takes 
place between the soil and the fertilizer. There is 
a general tendency for the soluble matter of fertilizers 
to undergo chemical change and become insoluble. 
This process is known as fixation. If a solution of 
potassium chloride be percolated through a column of 
clay, the filtrate will contain scarcely a trace of potas- 
sium chloride, but instead calcium and other chlo- 
rides. The element potassium of the potassium chlo- 
ride has been replaced by the element calcium present 
in the soil. As a result of this change between the 
two bases, an insoluble compound of potash is formed 
in the soil. 

203. Fixation Due to Zeolites. — It has been shown 
by experiments, particularly by those of Way and 
Voechler,53 that fixation is due mainly to zeolitic sili- 
cates (See section 62). Sandy soils containing but 
little clay have only feeble power of fixation. Clay 
soils when digested with hydrochloric acid to remove 
the zeolitic silicates, lose their power of fixation. 
The fixation of potassium chloride and the liberation 
of calcium chloride may be illustrated by the follow- 
ing reaction : 

Zeolite. Zeolite. 

AI2O3 "1 

Fe,^3 [-(SiO,)..H,0 + 2KCl=f^^^^ |- .(SiO,)..H,0 + CaCl, 
etc. J 




FIXATION l6l 

204. Humus May Cause Fixation. — Other com- 
pounds of the soil as humus and calcium carbonate 
also take an important part in fixation. In the case 
of humus, a union takes place betweenthe minerals 
in the fertilizers and the organic acids formed from 
the decay of the humus in the soil, resulting in the 
production of humates. (See Section 104.) 

205. Soils Possess Different Powers of Fixation. — 

All soils do not possess the power of fixation to the 
same extent. Heavy clays have the greatest fixative 
power while sandy soils have the least. Experi- 
ments have shown that in the first nine inches of 
soil, from 2,000 to 8,000 pounds per acre of potash 
and phosphoric acid may undergo fixation. ^^ Hence 
it is that a fertilizer, after being applied to a soil, may 
be entirely changed in composition, so that the plant 
feeds on the chemical products formed, rather than 
on the original fertilizer. 

206. Nitrates Cannot Undergo Fixation. — Nitro- 
gen in the form of nitrates or nitrites cannot undergo 
fixation. This is because all of the ordinary forms of 
nitrates are soluble. If potassium nitrate be added to 
a soil, calcium or sodium nitrate will be obtained as 
the soluble compound. The potassium undergoes fix- 
ation, but the nitrate radical does not. Chlorides also 
are incapable of undergoing fixation because all of the 
chlorides found in soils are soluble. 

207. Fixation of Ammonia. — Ammonium com- 
pounds readily undergo fixation, particularly in the 
presence of clay. (See experiment No. 15.) Theam- 



1 62 SOII.S AND FBRTII^IZERS 

monium radical, NH , like potassium is capable of re- 
placing soil bases. After undergoing fixation, the am- 
monium compounds readily yield to nitrification (See 
Section 145), lience they serve as a temporary but 
important form of insoluble nitrogen. The gen- 
eral tendency of the nitrogen compounds of the soil is 
to pass from insoluble to soluble forms through pro- 
cesses of decay, and to resist fixation changes. 

108. Fixation May Make Plant Food Less Avail- 
able. — If a liberal dressing of phosphate fertilizer be 
applied to a heavy clay soil, the phosphoric acid which 
is not utilized the first year or two may undergo fix- 
ation to such an extent that part becomes unavailable 
as plant food. It is not desirable to apply heavy 
dressings of fertilizers at long intervals because of fix- 
ation. It is always best to make lighter applications 
and more frequently. 

109. Fixation, a Desirable Property of Soils. — If 
it were not for the process of fixation, soils in regions 
of heavy rains would soon become sterile. On ac- 
count of the plant food being rendered insoluble, it is 
retained in the soil. The plant food which undergoes 
fixation is, as a rule, in an available condition or may 
readily become so by cultivation unless the soil be one 
of unusual composition. The process of fixation in 
the soil regulates the supply of plant food. Many 
fertilizers, if they did not undergo this process, would 
be injurious to crops for there would be an abnormal 
amount of soluble alkaline or acid compounds which 
would be destructive. The process of fixation first 
taking place removes, to a great extent, the injurious 



FIXATION 163 

water-soluble salts, particularly when the reaction is 
one of union rather than replacement. Then the plant 
is free to render soluble its own food in quantities 
and at times desired. 

Farm manures and commercial fertilizers alike un- 
dergo the process of fixation and, in studying ferti- 
lizers, their action upon the soil and the products of 
fixation are matters of prime importance. 

Soil water obtained by leaching soils is an exceed- 
ingly dilute solution of various mineral salts and organ- 
ic compounds. Through rock disintegration, mineral 
matter is rendered soluble, but the process of fix- 
ation prevents accumulation in the soil solution of 
compounds of such elements as potassium and phos- 
phorus. As a result of disintegration and fixation, 
numerous chemical changes take place in the soil, and 
the soil solution is an important factor in bringing about 
these reactions. Many of the phenomena which have 
been studied in connection with solutions in physical 
chemistry, take place in the soil. Diffusion, absorption, 
osmotic pressure and ionization, ^^ — disassociation of the 
molecule in solution, — all occur in soils and are due 
largely to the physical and chemical action of the soil 
solution. The soil solution from different soils varies 
with the composition and disintegration of the soil ; 
in the same soil at different times variations in the 
composition of the soil solution are noticeable. The soil 
solution is more important as an agent in bringing 
about chemical and physical changes in the soil than 
as a storehouse of planj: food. 



CHAPTER VII 



PHOSPHATE FERTILIZERS 

210. Importance of Phosphorus as Plant Food. — 

Phosphorus iu the form of phosphates is one of the 
essential elements of plant food. None of the higher 
orders of plants can complete their 
growth unless supplied with this 
element in some form. The illus- 
tration (Fig. 31) shows an oat plant 
which received no phosphates, but 
was supplied with all of the other 
elements of plant food. As soon as 
the phosphates stored up in the 
seed had been utilized, the plant 
ceased to grow, and after a few 
weeks, died of phosphate starvation, 
having made the total growth 
shown in the illustration. All crops 
demand their phosphates at an early 
stage in their development. Wheat 
Fig. 31. takes up eighty per cent, of its 

Oat plant grown phosphoric acid in the first half of 

without phosphorus , . . ^ , ., - 

the growing period, ^7 while clover 
has assimilated all of its phosphoric acid by the 
time the plant reaches full bloom. ^3 Phosphates ac- 
cumulate, to a great extent, in the seeds of grains and 
hence are sold from the farm when grain farming is 
extensively followed. All crops are very sensitive to 




PHOSPHATE FKRTILIZERS 165 

the absence of phosphates ; an imperfect supply re- 
sults in the production of light weight grains. The 
nitrogen and phosphates are to a great extent stored 
up in the same parts of the plant, particularly in the 
seed, which is richer in both nitrogen and phosphorus 
than is any other part. Nitrogen is the chief element 
of protein, while phosphorus is necessary to aid in 
transporting the protein compounds through the cell 
walls of plants. In speaking of the phosphorus in 
plants and in fertilizers, as well as in soils, the term 
phosphoric acid or phosphoric anhydride is used. 
This is because phosphorus is an acid-forming ele- 
ment and, as already explained, the anhydride of the 
element is always considered instead of the element 
itself. 

211. Amount of Phosphoric Acid Removed in 
Crops. — The amount of phosphoric acid removed 
in an acre of different farm crops ranges from 1 8 to 30 
pounds : 

Phosphoric acid 
per acre. 
Lbs. 

Wheat, 20 bu 12.5 

Straw, 2,000 lbs 7,5 

Total 20.0 

Barley, 40 bu 15 

Straw, 3,000 lbs 5 

Total 20 

Oats, 50 bu 12 

Straw, 3,000 lbs 6 

Total 18 



1 66 SOII.S AND FERTILIZERS 

Phosphoric acid 
per acre. 
Lbs. 

Corn, 65 bu 18 

stalks, 4, ODO lbs 4 

Total 22 

Peas, 3,500 lbs 25 

Red Clover, 4,000 lbs 28 

Potatoes, 150 bu 20 

Flax, 15 bu 15 

Straw, 1,800 lbs 3 

Total 18 

212. Amount and Source of Phosphoric Acid in 
Soils. — To meet the demand of growing crops for 25 
pounds of phosphoric acid per acre, there are present 
in soils from 1,000, and less, to 8,000 pounds of phos- 
phoric acid per acre, of which, however, only a frac- 
tion is available as plant food at any one time. The 
availability of phosphoric acid is a factor which has a 
great deal to do in determining crop-producing power. 
Many soils contain a large amount of total phosphoric 
acid which has become unavailable, because of poor 
cultivation and the absence of stable manure and lime 
to combine with the phosphates and render them 
available. 

The phosphates in soils are derived mainly from 
the disintegration of phosphate rock and from the 
remains of animal life. The phosphate deposits 
found in various localities are supposed to have been 
derived either from the remains of marine animals or 
from sea-water highly charged with soluble phos- 



PHOSPHATK FKRTII.IZERS 1 67 

phates. These deposits have been subjected to 
various geological and climatic changes which have 
resulted in the formation of soft phosphate, pebble 
phosphate and rock phosphate.^3 

213. Commercial Forms of Phosphoric Acid. — The 

commercial sources of phosphate fertilizers are : (i) 
phosphate rock, (2) bones and bone preparations, (3) 
phosphate slag and (4) guano. With the exception 
of phosphate slag and guano, the prevailing form of 
phosphorus is tricalcium phosphate. Before being 
used for commercial purposes, the tricalcium phos- 
phate, which is insoluble and unavailable, is treated 
with sulphuric acid which produces monocalcium 
phosphate, a soluble and available form of plant food. 

Ca^ (PO^X + 2H,SO^ + sUfi = CaH (PO;, + H^ + 
2CaSO ,2H O. 

In making phosphate fertilizers from bones or phos- 
phate rock an excess of the rock is used so that there 
will be no free acid in the fertilizer to be injurious to 
vegetation. 

The usual form in which calcium phosphate is 
found in nature is tricalcium phosphate, Ca (PO )^. 
Unless associated with organic matter or salts which 
render it soluble it is of but little value as plant food. 
When tricalcium phosphate is treated with sulphuric 
acid, monocalcium phosphate, CaH (PO )^, is formed. 
This compound is soluble in water and directly avail- 
able as plant food. When tricalcium and monocal- 
cium phosphate are brought together in a moist con- 
dition, dicalcium phosphate is produced. 



I68 . SOILS AND FERTILIZERS 

Ca/PO;, + CaH (PO;, = 2Ca H^(PO^)^. 
Another form of phosphate of lime, met with in basic 
phosphate slag, is tetracalcium phosphate, (CaO)^P^O^. 

214. Reverted Phosphoric Acid. — When mono- and 
tricalcium phosphate react, the product is known as 
reverted phosphoric acid, which is insoluble in water, 
but is not in such form as to be unavailable as plant 
food. It is generally considered that the reverted 
phosphoric acid is available as plant food. It is 
soluble in a dilute solution of ammonium citrate, and 
is sometimes spoken of as citrate-soluble phosphoric 
acid. Citrate-soluble phosphoric acid may also be 
formed by the action, upon the monocalcium phos- 
phate, of iron and aluminum compounds present as 
impurities in the phosphate rock. This process is a 
fixation change, as described in Chapter VI. In an 
old fertilizer there may be present citrate-soluble phos- 
phoric acid in two forms, as dicalcium phosphate and 
as hydrated phosphates of iron and aluminum. The 
citrate-soluble phosphoric acid in fertilizers is not all 
equally valuable as plant food because of the different 
phosphate compounds that may be dissolved by this 
solvent. 

215. Available Phosphoric Acid. — As applied to 
fertilizers, the term available phosphoric acid includes 
the water-soluble and citrate-soluble phosphoric acid. 
These solvents do not, under all conditions, make a 
sharp distinction as to the available and unavailable 
phosphoric acid when it comes to plant growth. 
Some forms of bones which are insoluble in an am- 



PHOSPHATE FERTILIZERS 1 69 

monium citrate solution are available as plant food, 
and then again some forms of aluminum phosphate 
which are soluble are of but little value as plant food. 
The terms available and unavailable phosphoric acid, 
as applied to commercial fertilizers, refer to the 
solubility of the phosphates, and as a general rule the 
value of the phosphates as plant food is in accord with 
their solubility. The more insoluble the less valu- 
able the material. 

216. Phosphate Rock.— Phosphate rock is found 
in many parts of the United States, particularly in 
South Carolina, North Carolina, Florida, Virginia 
and Tennessee. The deposits occur in stratified veins, 
as well as in beds and pockets. There are different 
types of phosphates as hard rock, soft rock, land 
pebble and river pebble. The pebble phosphates are 
found either on land or collected in cavities in the 
water courses, and are generally spherical masses of 
variable size. The soft rock phosphate is easily 
crushed, while the hard rock requires pulverizing with 
rock crushers. Phosphate rock usually contains from 
40 to 70 per cent, of calcium phosphate, the equiva- 
lent of from 17 to 30 per cent, phosphoric acid. The 
remaining 30 to 60 per cent, is composed of fine sand, 
limestone, alumina and iron compounds, with other 
impurities, which often render a phosphate unsuitable 
for manufacture into high-grade fertilizer. Raw phos- 
phate rock is sold at the mines for from $1.75 to $4.50 
per ton. 

217. Superphosphate. — Pulverized rock phosphate 



lyo SOII.S AND FERTII.IZERS 

known as phosphate flour, is treated with commercial 
sulphuric acid to obtain soluble monocalcium phos- 
phate. The amount of sulphuric acid used is deter- 
mined by the composition of the rock. Impurities as 
calcium carbonate and calcium fluoride react with sul- 
phuric acid and cause a loss of acid. Ordinarily, a 
ton of high-grade phosphate rock requires a ton of 
sulphuric acid. The mixing is done in lead-lined 
tanks. A weighed amount of phosphate flour is 
placed in the tank, and the sulphuric acid added, 
through lead pipes, from the acid tower. The mixing 
of the acid and phosphate is done with a mechanical 
mixer, driven by machinery. From the mixing tank 
the material is passed into other large tanks, where 
two or three days are allowed for the completion of 
the reaction. When the mass solidifies, it is ground 
and sold as superphosphate. In the manufacture of 
superphosphate, gypsum (CaSO .2H^0) is always pro- 
duced. A ton of superphosphate prepared from high- 
grade rock in the way outlined will contain about 40 
per cent, of lime phosphate, equivalent to 18 per cent, 
phosphoric acid. If a poorer quality of rock is used 
a proportionally smaller amount of phosphoric acid is 
obtained. A more concentrated superphosphate is ob- 
tained by producing phosphoric acid from the phos- 
phate rock, and then allowing the phosphoric acid to 
act upon fresh portions of the rock, the reactions be- 
ing as follows : ^"^ 

Ca/PO;, + 3H3SO^ = sCaSO, + zH/PO;. 
Ca(PO;, + 4H3P0^3HO = 3[CaH (PO^^.H O]. 
Ca (PO ),+ 2H P0^+ i2Hp=3[Ca H,(P0^),,4H O]. 



PHOSPHATE FERTILIZERS 171 

The phosphoric acid is separated from the gypsum be- 
fore acting upon the phosphate flour. In this way, 
superphosphate containing from 35 to 45 per cent, 
of phosphoric acid is produced. When fertilizers are 
to be transported long distances this concentrated 
product is preferable. The terms ' acid ' and ' super- 
phosphate ' have been generally used to designate 
both the first product produced by the action of sul- 
phuric acid and that produced by phosphoric acid, but 
of late there is a tendency to restrict the term ' acid 
phosphate ' to the product formed by the action of 
sulphuric acid, and the term ' super-phosphate ' to the 
concentrated product formed by the action of phos- 
phoric acid. 

218. Commercial Value of Phosphoric Acid. — The 
commercial value of phosphoric acid in fertilizers is 
determined by the value of the crude phosphate rock, 
cost of grinding and treating with sulphuric acid, and 
cost of transportation. The price of phosphoric acid 
in superphosphates usually ranges from 5 to 6 cents 
per pound. The field value, that is the increased 
yields obtained from the use of superphosphates, may 
not be in accord with the commercial value because so 
many conditions govern their use. The phosphoric 
acid obtained from feed-stuffs is usually considered 
worth about a cent a pound less than that from super- 
phosphates. Water-soluble phosphoric acid is general- 
ly rated a half cent per pound higher than citrate-sol- 
uble phosphoric acid. 

219. Phosphate Slag. — In the refining of iron ores 



172 SOILS AND FERTILIZERS 

by the Bessemer process, the phosphorus in the iron is 
removed as a basic slag. The lime, which is used as a 
flux, melts and combines with the phosphorus of the 
ore, forming phosphate of lime. The slag has a varia- 
ble composition. The process by which the phos- 
phorus of pig iron is removed and converted into basic 
phosphate slag is known as the Thomas process, and 
the product is sometimes called Thomas' slag. At the 
present time but little basic slag is produced for fer- 
tilizer purposes in this country. In Germany and 
some other European countries large amounts are 
used. Phosphate slag is ground to a fine powder and 
is applied directly to the land, without undergoing 
the sulphuric acid treatment. The phosphoric acid is 
present mainly in the form of tetracalcium phosphate, 
(CaO)^PO,. 

220. Guano is the Spanish for dung, and is a concen- 
trated form of nitrogenous and phosphate manure of 
interest mainly ori account of its historic significance. 
It is a mixture of sea-fowl droppings, accumulating 
along the seacoast in sheltered regions, with dead 
animals and debris, which has undergone fermen- 
tation. Guano and is concentrated in both nitro- 
gen and phosphoric acid. The introduction of guano 
into Europe marked an important period in agri- 
culture, inasmuch as its use demonstrated the action 
and importance of concentrated fertilizers. All of the 
best beds of guano have been exhausted and only a 
little of the poorer grades are now found on the mar- 
ket. The best qualities of guano contained from 12 



PHOSPHATE FERTILIZERS 1 73 

to 15 per cent, of phosphoric acid, lo to 12 per cent, 
of nitrogen, and from 5 to 7 per cent, of alkaline salts. 

BONE FERTILIZERS 

221. Raw Bones contain, in addition to phosphate 
of lime, Ca (PO )^, organic matter which makes them 
slow in decomposing and slow in their action as a fer- 
tilizer. Before being used as a fertilizer they should be 
fermented in a compost heap witli wood ashes in the 
following way, a protected place being selected so that 
no losses from drainage will occur. A layer of well- 
compacted manure is covered with wood ashes, the 
bones are then added and well covered with manure 
and wood ashes. From three to six months should 
be allowed for the bones to ferment. The large, coarse 
pieces may then be crushed and are ready for use. 
The presence of fatty material in a fertilizer retards its 
action because fat is so slow in decomposing. Bones 
from which the organic matter has been removed are 
more active as a fertilizer than raw bones. Bones 
contain from 18 to 25 per cent, of phosphoric acid and 
from 2 to 4 per cent, of nitrogen. The amount and 
value of the citrate-soluble phosphoric acid are extre- 
mely variable. 

222. Bone Ash is the product obtained when bones 
are burned. It is not extensively used as a fertilizer 
because of the greater commercial value of bone-black. 
It contains about 36 per cent, of phosphoric acid, and 
is more concentrated than raw bones. 

223. Steamed Bone. — Raw bones are subjected to 
superheated steam to remove the fat and ossein to be 



174 SOILS AND FERTILIZERS 

used for making soap and glue ; they are then pul- 
verized and sold as fertilizer under the name of bone 
meal, which contains from 1.5 to 2.5 per cent, of nitro- 
gen and from 22 to 29 per Lent, of phosphoric acid. 
Steamed bone makes a more active fertilizer than raw 
bone. Occasionally, well prepared bone meal is used 
for feeding pigs and fattening stock in the same way 
that flesh meal is used. 

224. Dissolved Bone. — When bones are treated 
with sulphuric acid as in the manufacture of super- 
phosphates the product is called dissolved bone. The 
tricalcium phosphate undergoes a change to more 
available forms, as described, and the nitrogen is ren- 
dered more ava'lable. Dissolved bone contains from 
2 to 3 pel c^nt. of nitrogen and from 15 to 17 percent, 
of phosphoric acid. 

225. Bone-black. — When bones are distilled bone- 
black is obtained. It is extensively employed for re- 
fining sugar, and after it has been used and lost its 
power of decolorizing solutions, it is sold as fertilizer. 
It contains about 30 per cent, phosphoric acid and is a 
concentrated phosphate fertilizer. 

226. Use of Phosphate Fertilizers. — The amount 
of phosphoric acid advisable to apply to crops, varies 
with the nature of the soil and the kind of crop to be 
produced. On a poor soil 400 pounds of acid-phos- 
phate per acre is an average application. It is usually 
applied as a top dressing just before seeding, and may 
be placed near the hills of corn or potatoes, but not in 
contact with the seed. It is not advisable to make 



PHOSPHATE FERTILIZERS 175 

heavy applications of siiperphosphates at long inter- 
vals, because the process of fixation may take place to 
such an extent that crops are unable to utilize the fer- 
tilizer. Lighter and more frequent applications, as 
lOO to 200 pounds per acre, are preferable. Phos- 
phates should not be mixed with lime carbonate 
before spreading ; ^^ it is best to apply the fertilizer 
directly to the land. Phosphates may be used in con- 
nection with farm manures. Many soils which con- 
tain liberal amounts of phosphoric acid are im- 
proved by phosphate dressing of 75 pounds per acre. 
Such soils, however, should be more thoroughly 
cultivated, and manured with farm manures, to 
make the phosphates available. There is frequently 
an apparent lack of phosphoric acid in a soil 
when in reality the trouble is due to other causes, 
as lack of organic matter to combine with the phos- 
phates or to a deficiency of lime. Before using phos- 
phate fertilizers, careful field tests should be made to 
determine if the soil is in actual need of available 
phosphoric acid. Directions for making these tests 
are given in Chapter X. 

227. How to Keep the Phosphoric Acid Available. 
— Phosphoric acid associated with organic matter in 
a moderately alkaline soil, is more available than that 
in acid soils. Soft phosphate rock may be mixed with 
manure or materials like cottonseed meal and made 
slowly* available for crops. Soils which contain a 
good stock of phosphoric acid, when kept well ma- 
nured, and occasionally limed if necessary, have a lib- 
eral supply of available phosphoric acid. As an illus- 



176 SOILS AND FERTILIZERS 

tration, the following example of two soils from ad- 
joining farms, which have been cropped and manured 
differently, may be cited i^^ 



Soil well manu 
and crops 
rotated. 


red 


No manure and 

continuous wheat 

raising. 


Per cent. 






Per cent. 


Total phosphoric acid 0.20 






0.20 


T-TnmiT;. ..... a •?? 






1.62 


Humic phosphoric acid-. 0.06 






0.02 



It is more economical to keep the insoluble phos- 
phoric acid of the soil in available forms by the use of 
farm manures, lime, rotation of crops and thorough 
cultivation, than it is to purchase superphosphates in 
commercial forms. 



CHAPTER VIII 



POTASH FERTILIZERS 

228. Potassium an Essential Element of Plant 
Food. — Potassium is one of the three elements most 

essential as plant food. In its ab- 
sence plants are unable to develop. 
Oats seeded in a sterile soil from 
which potash only was withheld 
made the total growth shown in 
the illustration (Fig. 32). When 
potash is present in the soil in 
liberal amounts and associated 
with other essential elements vig- 
orous plants are produced. Potash 
like phosphoric acid and nitrogen 
is utilized by crops in the early 
stages of growth. Potassium 
does not accumulate in seeds to 
the same extent as phosphoric 
acid and nitrogen, but is present 
mainly in stems and leaves, con- 
sequently when straw crops are 
utilized in producing manure the potash is not lost or, 
as in the case of nitrogen, sold from the farm. But 
with ordinary grain farming excessive losses of potash 
do occur, particularly when the straw is burned and 
the ashes are wasted. 

229. Amount of Potash Removed in Crops. — In 




Fig, 32. Oat plant 
grown without potash. 



(12) 



1 78 SOILS AND FERTILIZERS 

grain crops from 35 to 60 pounds of potash per acre 
are removed from the soil. For grass crops more pot- 
ash is required than for grains, while roots and tubers 
require more than grass. The approximate amount 
of potash removed in various crops is given in the 
following table :^^ 

Potash per acre 
Lbs. 

Wheat, 20 bu 7 

Straw, 2,000 lbs 28 

Total 35 

Barley, 40 bu 8 

Straw, 3,000 lbs - 30 

Total 38 

Oats, 50 bu 10 

Straw, 3,000 lbs 35 

Total 45 

Corn, 65 bu 15 

Stalks, 3,000 lbs 45 

Total 60 

Peas, 30 bu 22 

Straw, 3,500 lbs 3^ 

Total 60 

Flax, [5 bu 8 

Straw, 1,800 lbs 19 

Total 27 

Mangels, 10 tons > 150 

Meadow hay, i ton 45 

Clover hay, 2 tons 66 

Potatoes, 150 bushels 75 



POTASH FERTII.IZERS 1 79 

230. Amount of Potash in Soils. — In ordinary 
soils there are from 3,500 to 12,000 pounds of potash 
per acre to the depth of one foot. Many soils with 
apparently a good stock of total potash give excellent 
results when a light dressing of potash salts is applied. 
The amount of available potash in the soil is more 
difficult to estimate than the available phosphoric 
acid. There is a great difference in crops as to their 
power of obtaining potash. Some require greater 
help in procuring this element than others. A lack 
of available potash is sometimes indirectly due to a 
deficiency of lime or other alkaline matter in the soil, 
which prevents the necessary chemical changes taking 
place in order that the potash may be liberated as 
plant food. 

231. Sources of Potash in Soils. — The main 
source of the soil's potash is feldspar, which, after dis- 
integration, is broken up into kaolin and potash com- 
pounds. Mica and granite also, in some localities, 
contribute liberal amounts. A valuable source of 
potash are the zeolitic silicates. The amount of 
water-soluble potash in soils, except in alkaline soil, 
is extremely small. By the action of many fertilizers 
the potash compounds undergo changes in composition. 
For example, the gypsum which is always present in 
acid phosphates, liberates some potash. The potash 
compounds of the soil are in various degrees of com- 
plexity from forms soluble in dilute acids to insoluble 
minerals as feldspar. 

232. Commercial Forms of Potash. — Prior to the 



l8o SOILS AND FERTILIZERS 

introduction of the Stassfurt salts, wood ashes were 
the main source of potash. Since the discovery and 
development of the Stassfurt mines, the natural prod- 
ucts as kainit, and muriate and sulphate of potash have 
been extensively used for fertilizing purposes. A 
small amount of potash is obtained also from waste 
products as tobacco stems, cottonseed hulls, and the 
refuse from beet-sug-ar factories. 

STASSFURT SALTS 

233. Occurrence. ^4 — -Xhe Stassfurt mines were first 
worked with the view of procuring rock salt. The 
various compounds of potash, soda and magnesia, 
associated with the layers of rock salt, were regarded 
as troublesome impurities, and attempts were made by 
sinking new shafts to avoid them, but with the result 
of finding them in greater abundance. About 1864 
their value as potash fertilizer was established. It is 
supposed that at one time the region about the mines 
was submerged and filled with sea-water. The tropi- 
cal climate of that geological period caused rapid 
evaporation, which resulted in forming mineral depos- 
its, the less soluble material as lime sulphate being 
first deposited, then a layer of rock salt, and finally 
layers of potash and magnesium salts in the order of 
their solubility. 

234. Kainit is a mineral composed of potassium 
sulphate, magnesium sulphate, magnesium chloride 
and water of crystallization. As it comes from the 
mine it is mixed with gypsum, salt, potassium chlo- 
ride, and other bodies. Kainit contains from 12 to 



STASSFURT SALTS l8l 

12.50 per cent, potash, and is one of the most import- 
ant of the Stassfurt salts. It is extensively used as a 
potash fertilizer, and is also mixed with other mater- 
ials and sold as a commercial fertilizer. The mag- 
nesium chloride causes it to absorb water, and the 
presence of other compounds results in the formation 
of hard lumps, whenever kainit is kept for a long 
time. Kainit is soluble in water, and can be used as 
a top dressing at the rate of 75 to 200 pounds or more 
per acre. 

235. Muriate of Potash. — This material is exten- 
sively used as a fertilizer and is valuable for general 
garden and farm crops. It is a manufactured product 
and ranges in purity from 60 to 95 per cent, of potas- 
sium chloride, equivalent to from 35 to 60 per cent, of 
potash, the chief impurity being sodium chloride. 
Potassium chloride is readily soluble and is a quick 
acting fertilizer. When us^d in large amounts, mu- 
riate of potash and other chlorides may unfavorably 
affect the quality of some, crops as potatoes, sugar 
beets and tobacco. Ordinarily, muriate of potash is 
one of the cheapest and most active forms of potash 
and can be used as a top dressing at the rate of 200 
pounds or more per acre when preparing soils for 
crops. It is valuable for grass and grain crops, and 
has given good results on pasty lands.93 

236. Sulphate of Potash. — High-grade sulphate 
of potash is prepared from some of the crude Stassfurt 
salts, and may contain as high as 97 per cent. K^SO . 
Low-grade sulphate of potash is about 90 per cent, 
pure. High-grade sulphate of potash contains about 



l82 SOILS AND FERTILIZERS 

50 per cent, of potassium oxide (K^O), and is one of 
the most concentrated forms of potash fertilizer. It 
is particularly valuable because it can be safely used 
on crops as tobocco and potatoes which would be in- 
jured in quality if muriate of potash were applied, or 
if much chlorine were present. 

237. Miscellaneous Potash Salts. — Carnallit, 9 per 
cent. Kp,— composed of KCl,MgCl^,6Hp. Poly- 
halit, 15 per cent. K^, — composed of K^SO^,MgSO^. 
(CaSO X,Hp. Krugit, 10 per cent. K^, — composed 
of K^s6^,MgS0^,(CaS0^)^,Hp. Sylvinit, 16 to 20 
per cent. K^, — composed of KCl,NaCl and impur- 
ities. Kieserit, 7 per cent. K^, — composed of 
MgSO and carnallit. 

238. Wood Ashes. — For ordinary agricultural pur- 
poses, wood ashes are an important source of potash. 
Ashes are exceedingly variable in composition. 
When leached the soluble salts are extracted and 
there is left only about i per cent, of potash. In un- 
leached ashes the amount of potash ranges from 2 to 
10 per cent. Soft wood ashes contain much less 
potash than hard wood ashes. Goessmann gives the 
following as the average of 97 samples of ashes :^^ 

Average composition. Range. 

Per cent. ^ Per cent. 

Potash 5.5 2.5 to 10.2 

Phosphoric acid 1.9 0.3 to 4.0 

Lime 34.3 18.0 to 50.9 

IN 10,000 POUNDS OF WOOD. 

Potash. Phosphoric acid. 

Lbs. Lbs. 

White oak 10.6 2.5 

Red oak 14.0 6.0 

Ash 15.0 I.I 

Pine 0.8 0.7 

Georgia pine 5.0 1.2 

Dogwood .' 9.0 5.7 



WOOL ASHKS 183 

239. Action of Ashes on Soils. — Ashes act upon 
soils both chemically and physically. They are usu- 
ally regarded as a potash fertilizer only, but they also 
contain lime and phosphoric acid, and may be very 
beneficial in supplying these elements. The potash 
is present mainly as potassium carbonate. Ashes are 
valuable, too, because they add alkaline matter to the 
soil, which corrects acidity and aids nitrification. A 
dressing of ashes improves the mechanical condition 
of many soils by binding the soil particles. This 
property is well illustrated in the so-called "Gumbo" 
soils, which contain so much alkaline matter that the 
soil has a soapy taste and appearance, and when plowed 
the particles fail to separate. 

240. Leached Ashes. — When ashes are leached the 
soluble salts are extracted ; the insoluble matter 
which is left is composed mainly of calcium carbonate 
and silica.^^ 

Unleached ashes. Leached ashes. 

Per cent. Per cent. 

Water 12.0 30.0 

Silica, etc 13.0 13.0 

Potassium carbonate 5.5 i.i 

Calcium " 61.0 51.0 

Phosphoric acid 1.9 1.4 

241. Alkalinity of Leached and Unleached Ashes. 

— A good way to detect leached ashes is to deter- 
mine the alkalinity in the following way : Weigh 
out 2' grams of ashes into a beaker, add 100 cc. dis- 
tilled water, and heat on a sand-bath nearly to boiling, 
cool and filter. To 50 cc. of the filtrate add about 3 
drops of cochineal indicator, and then a standard solu- 



1 84 SOILS AND FERTILIZERS 

tion of hydrochloric acid from a burette until the solu- 
tion is neutral. If a standard solution of acid cannot 
be procured, one containing 15CC. concentrated hydro- 
chloric acid per liter of distilled water may be used for 
comparative purposes. Leached ashes require less than 
2 cc. of acid to neutralize the alkaline matter in i gram 
while unleached ashes require from 10 to 18 cc. In pur- 
chasing wood ashes, if a chemical analysis cannot be 
secured, the alkalinity of the ash should be determined. 

242. Coal and other Ashes. — Since the amount of 
phosphoric acid and potash in coal ashes is very small, 
they have but little fertilizer value. Soft-coal ashes 
contain more potash than those frofti hard coal, but it 
is held in such firm combination as to be of but 
little value. 

The ashes from sawmills where soft wood is burned 
and the ashes are unprotected, are nearly worthless. 
When peat-bogs are burned over, large amounts of ashes 
are produced. If the bogs are covered with timber, 
the ashes are sometimes of sufficient value to warrant 
their transportation and use. 

Phosphoric 
Potash ^ acid. 

Per cent. Per cent. 

Hard coal ashes o.io o.io 

Soft coal ashes-. 0.40 0.40 

Sawmill ashes^^ 1.20 i.oo 

Peat-bog ashes^* i . 15 0.54 

Peat-bog ashes (timbered)^* 3.68 2.56 

Tobacco stem ash 4.00 7.00 

Cottonseed hulls, ash 20.00 7.00 

243. Commercial Value of Potash. — The market 
value of potash is governed by the selling price of 



USE OF POTASH FERTILIZERS 1 85 

high-grade sulphate of potash and kainit. Ordinarily, 
the price per pound of potash varies from 4 to 5 cents. 
As in the case of nitrogen and phosphoric acid, the 
market and field values as determined by crop yields 
may be entirely at variance. Before potash salts are 
used, careful field tests should be made to determine 
the actual condition of the soil as to its need of potash. 
(See chapter X, Commercial Fertilizers.) 

244. Use of Potash Fertilizers. — Wood ashes or 
Stassfurt salts should not be used in excessive amounts. 
Not more than 300 pounds per acre should be applied 
unless the soil is known to be markedly deficient in 
potash, and previous tests indicate that larger amounts 
are safe and advisable. Potash fertilizers should be 
evenly spread and not allowed to come in direct con- 
tact with plant roots. They should be used early in 
the spring before seeding or before the crop has made 
much growth. Wood ashes make an excellent top 
dressing for grass lands, particularly where it is de- 
sired to encourage the growth of clover. There are 
but few crops or soils that are not greatly benefited by 
a light application of wood ashes, and none should 
ever be allowed to leach or waste about a farm. 

245. Joint Use of Lime and Potash. — When a pot- 
ash fertilizer is used, a dressing of lime will frequently 
be beneficial. The potash undergoes fixation, and when 
it is liberated there should be some basic material as 
lime to take its place. Goessmann observed that land 
manured for several years with potassium chloride 
finally produced sickly crops, but that an application 



l86 SOILS AND FERTILIZERS 

of slaked lime restored a healthy appearance to suc- 
ceeding crops.^7 If the soil is well stocked with lime 
its joint use with potash fertilizers is not necessary ; 
if it is acid, lime should be used to correct the acidity 
before the potash is applied. The use of potash fer- 
tilizers for special crops is discussed in Chapter lo. 



CHAPTER IX, 



LIME AND MISCELLANEOUS FERTILIZERS 



246. Calcium an Essential Element of Plant Food. 

— Calcium is present in the ash of all plants, and is 

usually more abundant in soils than phosphorus or 
potassium. It takes an essential 
part in plant growth, and when- 
ever withheld growth is checked. 
The effect of withholding cal- 
cium is shown in the illustration 
(Fig. 33), which gives the total 
growth made by an oat plant 
under such a condition. 

Plants grown on soils deficient 
in calcium compounds, lack hard- 
iness. They are not so able to 
withstand drought or unfavorable 
climatic conditions, as plants 
grown on soils well supplied with 
this element. Calcium does not 
accumulate in the seeds of plants, 
but is present mainly in the leaves 
and stems where it takes an im- 
portant part in the production 
of new tissue. The term lime, 

used in connection with crops and soils refers to their 

content of calcium oxid. 




33- 



'Fig. 
Oat plant grown with- 
out calcium. 



l88 SOILS AND FERTILIZERS 

247. Amount of Lime Removed in Crops. 3^ — 

Pounds per acre. 

Wheat, 20 bushels i 

Straw, 2000 pounds - 7 

Total 8 

Corn, 65 bushels i 

Stalks, 3000 pounds r r 

Total 12 

Peas, 30 bushels • • • . • 4 

Straw, 3500 pounds • • • 71 

Total 75 

Flax, 15 bushels 3 

Straw, 1800 pounds ..• • 13 

Total l6 

Clover, 4000 pounds 75 

Clover and peas remove so much lime from the soil 
that they are often called lime plants. The amount 
required by grain and hay is small compared with that 
required by a clover or pea crop. 

248. Amount of Lime in Soils. — There is no other 
element in the soil in such variable amounts as cal- 
cium. It may be present from a few hundredths of a 
per cent, to twenty per cent, or more. Soils which 
contain from 0.4 to 0.5 per cent, of lime as carbonate 
are usually well supplied. The lime in a soil takes 
an important part in soil fertility ; when deficient, 
humic acid may be formed, nitrification checked, and 
the soil particles will lack binding material. 

249. Different Kinds of Lime Fertilizers. — By the 
term 'lime fertilizer' is usually meant land plaster 
(CaSO ,2H^0). Occasionally quicklime (CaO) and 



LIME FERTILIZERS 189 

slaked lime (Ca [OH] ^) are used on very sour land. In 
general a lime fertilizer is one which supplies the 
element calcium ; common usage, however, has re- 
stricted the term to sulphate of lime. 

250. Action of Lime Fertilizers upon Soils. — Lime 
fertilizers act both chemically and physically. Chem- 
ically, lime unites with the organic matter to form 
humate of lime and thus prevents the formation of 
humic acid. It aids in nitrification and acts upon 
the soil, liberating potassium and other elements of 
plant food. Physically, lime improves capillarity, 
precipitates clay when suspended in water, and pre- 
vents losses, as the washing away of fine earth. 

251 . Action of Lime upon Organic Matter. — When 
soils are deficient in lime, an acid condition may de- 
velop to such an extent as to be injurious to vegeta- 
tion. Nitrogen, phosphoric acid, and potash may all 
be present in liberal amounts, but in the absence of 
lime poor results will be obtained. Experiments by 
Wheeler at the Rhode Island Experiment Station in- 
dicate that there are large areas of acid soils in the 
Eastern States which are much improved when treat- 
ed with air-slaked lime.^^ There is great difference 
in the power of plants to live in acid soils. Some 
agricultural crops as legumes are particularly sensi- 
tive, while many w^eeds have such strong power of 
endurance that they are able to thrive in the presence 
of acids. Weeds frequently reflect the character 
of a soil as to acidity, in the same way that an "alkali" 
soil is indicated by the plants produced. 



I90 SOIIvS AND FERTILIZERS 

252. Lime Liberates Potash. — The action of lime 
upon soils well stocked with potash results in the fixa- 
tion of the lime and the liberation of the potash; the 
reaction takes place in accord with the well-known 
exchange of bases as explained in the chapter on 
fixation. The extent to which potash may be liber- 
ated by lime depends upon the firmness of chemical 
combination with which the potash is held in the 
soil. Boussingault found that when clover was 
limed there was present in the crop three times as 
much potash as in a similar crop not limed. His re- 
sults are as follows :^9 

Kilos per hectare. 
In crop not limed. In limed crop. 

First Second First Second 

year. year. year. year. 

Lime-.^. 32.2 32.2 79.4 102.8 

Potash 26.7 28.6 95.6 97.2 

Phosphoric acid. 11. o 7.0 24.2 22.9 

The indirect action of land plaster upon Western 
prairie soils in liberating plant food, particularly 
potash and phosphoric acid, is unusually marked. 
Laboratory experiments show that small amounts of 
gypsum are quite active in rendering potash, phos- 
phoric acid, and even nitrogen soluble in the soil 
water.5 Occasionally applications of superphosphate 
fertilizers give large yields due to the gypsum which 
they contain, and not to the phosphorus. 

253. Quicklime and Slaked Lime. — When it is de- 
sired to correct acidity slaked lime is used. Air- 
slacked lime is not as valuable as water-slaked lime. 
Quicklime cannot be used on land after a crop has 



LIME FERTILIZERS 19I 

been seeded. Both slaked lime and quicklime 
should be applied some little time before seeding 
and not to the crop. Tne action of quicklime upon 
organic matter is so rapid that it destroys vegetation. 
Slaked lime is less injurious to vegetation. 

254. Pulverized Lime Rock. — In some localities 
pulverized lime rock is used. It may be applied as a 
top-dressing in almost unlimited amounts. It is most 
beneficial on light, sandy soils, where it performs the 
function of fine clay as well as being beneficial in its 
chemical action. It is also beneficial on acid sods. 
Not all soils are alike responsive to applications of 
limestone, and before using, it is best to determine 
to what extent it will be beneficial. There are no 
conditions where limestone is injurious to soil or crop, 
and it is frequently very beneficial. 

255. Marl. — Underlying beds of peat, deposits of 
marl are occasionally found. Marl is a mixture of 
disintegrated limestone and clay, and contains varia- 
ble amounts of calcium carbonate, phosphoric acid, 
and potash. When peat and marl are found together 
they may be used jointly with manure as described in 
Section 169. Many sandy lands in the vicinity of peat 
and marl deposits would be greatly improved, both 
physically and chemically, by the use of these materials. 

256. Physical Action of Lime .— The addition of 
lime .fertilizers to sandy soils improves their general 
physical condition. Heavy clays lose their plasticity 
when limed ; the fine clay particles are cemented 
and act as sand, which improves the mechanical 



192 SOILS AND FERTILIZERS 

condition of the soil. The physical action of lime 
in soils is well illustrated in the case of 'loess soils/ 
which are composed of clay and limestone. The lime 
cements the clay particles and forms compound grains, 
making the soil more permeable, and more easily 
tilled. The improved physical condition alone which 
follows the application of lime fertilizers, is frequently 
sufficient to warrant their use. 

257. Application of Lime Fertilizers, — Lime is 
generally used as a top-dressing on grass lands at the 
rate of 200 to 500 pounds per acre. Excessive appli- 
cations are undesirable. Lime as gypsum is particu- 
larly valuable when applied to land where crops are 
grown which assimilate large amounts of lime. It 
should be remembered that it is not a complete ferti- 
lizer but simply an amendment and an indirect ferti- 
lizer. '° If used to excess it may get the soil in such 
condition that plant food is not easily rendered avail- 
able. A common saying is " Lime makes the father 
rich but the son poor."^^ This is true, however, only 
when lime is used in excess. When used occasion- 
ally in connection with other manures, it has no injur- 
ious effect upon the soil and is a valuable fertilizer, 
especially where clover is grown with difficulty. 

MISCELLANEOUS FERTILIZERS 

258. Salt is frequently used as an indirect fertilizer. 
Sodium and chlorine, the two elements of which it is 
composed, are not absolutely necessary for. normal 
plant growth. When salt is applied to the soil and 
the sodium undergoes fixation, potassium may be lib- 
erated. An early experiment of Wolff illustrates this 



MISCELLANEOUS FERTILIZERS 1 93 

point : a buckwheat plot fertilized with salt produced 
a crop with more potash and less sodium than a sim- 
ilar unfertilized plot. 

Salt may be used to check the rank growth of straw 
during a rainy season, and thus prevent loss of the 
crop by lodging. It should not be used in excessive 
amounts, as it is destructive to vegetation; 200 pounds 
per acre is a fair application. Salt also improves the 
physical condition of the soil by increasing the surface- 
tension of the soil water. It should not be used on a 
tobacco or potato crop, because it injures the quality 
of the product. Salt is beneficial in preventing some 
forms of fungus diseases from becoming established 
in soils. 

259. Magnesium Salts. — Magnesium is present in 
the ash of all plants, and is an essential element of 
plant growth. Usually soils are so well stocked with 
this element that it is not necessary to apply it in fer- 
tilizers. Some of the magnesium salts, as the chloride, 
are injurious to vegetation, but when associated with 
lime as carbonate, magnesia imparts fertility. In 
many of the Stassfurt salts magnesium is present. 

260. Salt. — The deposits formed in boiler flues and 
chimneys when wood and soft coal are burned contain 
small amounts of potash and phosphoric acid. Soot 
is valuable mainly as a mechanical fertilizer and is 
slow in decomposing. There is but little plant food 
in soot, as shown by the following analysis: 

Soft coal soot. Hard wood soot. 

Per cent.i'i Per cent. vo 

Potash 0.84 1.78 

Phosphoric acid 0.75 0.96 

(r3) 



194 SOILS AND FERTILIZERS 

261. Seaweeds. —Seaweeds are rich in potash and 
near the sea coast are extensively used for fertilizer. 

Composition of 

mixed seaweeds. 

Per centJO 

Water 81.50 

Nitrogen 0.73 

Potash 1 .50 

Phosphoric acid 0.18 

262. Strand Plant Ash. — Weeds and plants pro- 
duced on waste land along the sea are in many Euro- 
pean countries burned and the ashes used as fertilizer 
on other lands. By this means waste land is made to 
produce fertilizer for fields which are tillable. The 
amount of fertility removed in weeds is usually greater 
than that in agricultural plants, because weeds have 
greater power of obtaining food from the soil. When 
wheat or other grain is raised, and a small crop of 
grain and a large crop of weeds are the result, there 
is more fertility removed from the soil than if a heavy 
stand of grain had been obtained. The ashes of strand 
plants and weeds are extremely variable in composi- 
tion. 

263. Wool Washings and Waste — The washings 
from wool contain sufficient potash to make them 
valuable as fertilizer. In wool there is a high 
per cent, of potash, which is soluble,- and readily re- 
moved in the washings. Wool waste may contain 
from I to 5 per cent, of potash and from 4 to 7 per 
cent, of nitrogen in somewhat inert forms. 

264. Street Sweepings. — The horse manure and 
debris collected from paved streets in cities and known 



MISCELLANKOUS FERTILIZERS 1 95 

as street sweepings have some value as fertilizer, and 
are occasionally used for market gardening purposes. 
Street sweepings, because of the loss of the liquid ex- 
crements, have a lower value than average stable 
manure. They cannot be used economically when 
labor and the cost of hauling are high-priced, or when 
a quick-acting manure is desired. For sanitary rea- 
sons, the use of street sweepings is not always desir- 
able, as mixed with the horse droppings frequently 
there are associated accumulations of filth from dwell- 
ings contaminated with disease producing germs. 
Crude garbage has a low manurial value, but when 
sorted and cremated, the burned residue can be used 
to better advantage as a fertilizer than the raw gar- 
bage, and is without the objectionable and unsanitary 
features. 



CHAPTER X 

COMMERCIAL FERTILIZERS AND THEIR USE 

265. Development of the Commercial Fertilizer 
Industry. — The commercial fertilizer industry owes 
its origin to Leibig's work on plant ash. The first 
superphosphate was made by Sir J. B. Lawes, about 
1840, from spent bone black and sulphuric acid. His 
interest had previously been attracted to the use of 
bones by a gentleman who farmed near him, "who 
pointed out that on one farm bone was invaluable for 
the turnip crop, and on another farm it was useless. "^4 
Since i860 the commercial fertilizer industry in this 
country has developed rapidly, until now the amount 
of money expended in purchasing commercial ferti- 
lizers and amendments is estimated at $60,000,000 
annually. Nearly all of this sum is expended in less 
than a quarter of the area of the United States. 

266. Complete Fertilizers and Amendments. — The 
term commercial fertilizer is applied to those materials 
made by mixing different substances which contain 
plant food in concentrated forms. When a commer- 
cial fertilizer contains nitrogen, phosphoric acid, and 
potash, it is called a complete fertilizer, because it 
supplies the three elements which are most liable 
to be deficient. Materials as sodium nitrate which 
supply only one element are called amendments. 
It frequently happens that a soil requires only one 
element in order to produce good crops. In such 



COMMERCIAL FERTILIZERS 1 97 

cases only, the one element needed should be supplied. 
Complete fertilizers are sometimes used when the 
soil is only in need of an amendment. 

267. Variable Composition of Commercial Ferti- 
lizers. — Since commercial fertilizers are made by mix- 
ing various materials which contain different amounts 
of nitrogen, phosphoric acid, and potash, it follows 
that they are extremely variable in composition and 
value. 'No two samples are the same, hence the im- 
portance of knowing the composition of every separate 
brand purchased. The composition of fertilizers is 
varied to meet the requirements of different soils and 
crops. Some fertilizers are made rich in phosphoric 
acid, while others are rich in nitrogen and potash. 

268. How a Fertilizer is Made. — The most com- 
mon materials used in making complete fertilizers 
are : Nitrate of soda, kainit, and dissolved phosphate 
rock. These materials have about the following com- 
position : 

Nitrate of soda 15.5 per cent, nitrogen. 

Kainit 12.5 per cent, potash. 

Dissolved phosphate • . • 14.0 per cent, phosphoric acid. 

The fertilizer may be made rich or poor in an}^ one 
element. Many fertilizers contain about twice as 
much potash as nitrogen and five times as much phos- 
phoric acid as potash. In order to make a ton of such 
a fertilizer it would be necessary to take : 

Pounds. 

Nitrate of soda 225 

Kainit 425 

Phosphate • 1350 



198 SOILS AND FERTILIZERS 

The ton of fertilizer would then contain about 35 
pounds of nitrogen, 189 pounds of phosphoric acid 
and 53 pounds potash. These amounts are deter- 
mined by multiplying the percentage composition by 
the weight of material taken : 

Pounds. 

Nitrogen 225X0.155= 34.9 

Potash 425 X o. 125 = 53. 1 

Phosphoric acid 1350 X 0.14 =189.0 

The fertilizer would then contain approximately 1.75 
per cent, nitrogen, 2.65 per cent, potash, and 9.45 per 
cent, phosphoric acid. The percentage amounts are 
obtained by dividing the total pounds by 20. This 
fertilizer, if made at home from materials purchased 
in the market, would cost, exclusive of transportation 
and mixing, $18.79. 

Pounds. Cost. 

Nitrogen 34-9 @ I4>^ cents = ^5.06 

Phosphoric acid 189.0 @ 6 cents ^11.34 

Potash 53.1 @ 4>^ cents = 2.39 

Total I18.79 

A more concentrated fertilizer could be prepared by 
using high-grade sulphate of potash, superphosphate, 
and ammonium sulphate. A fertilizer composed of 
these ingredients would contain : 



C g N 

Total g S'S 

Pounds. Percent. pounds. Value, p^u-it 

300 Sulphate of ammonia 20 N 60 @ 14^^ cents = I8.70 3.00 

500 Sulphate of potash . . 50 KgO 250 @ 4^ cents = 11.25 12.50 

1200 Superphosphate ... . 35 P2O5 420 @ 6 cents = 25.20 21.00 

Total I45.15 



COMMERCIAL FERTILIZERS 199 

So concentrated a fertilizer as the preceeding is 
rarely, if ever, found on the market, although the 
price, $45.15 per ton, is frequently charged. This 
example is given to show the composition and cost 
of one of the most concentrated fertilizers that can 
be produced. 

Any one of the different materials mentioned in the 
chapters on special fertilizers could be used in making 
commercial fertilizers, as dried blood, tankage, nitrate 
of soda, sulphate of ammonia, raw bone, dissolved 
bone, raw phosphate rock, dissolved phosphate rock, 
basic slag, kainit, muriate or sulphate of potash, and 
many others. Inasmuch as each of these materials 
has a different value, it follows that fertilizers, even 
of the same general composition, may have widely 
different crop-producing powers. 

269. Inert Forms of Plant Food in Fertilizers.— 

A fertilizer of the same general composition as the first 
example could be made from feldspar rock, apatite 
rock, and leather. The leather contains nitrogen, 
the apatite contains phosphoric acid, and the feldspar 
potash. Such a fertilizer would have no value when 
used on a crop, because all of the plant food elements 
are present in unavailable forms. Hence, in purchas- 
ing fertilizers, it is necessary to know not only the 
percentage composition, but also the nature of the 
materials from which the fertilizer was made. Inert 
forms of plant food are akin to indigestible forms of 
animal food ; in each it is the part which is assimi- 
lated that is of value. 



200 SOILS AND FERTILIZERS 

270. Inspection of Fertilizers. — In many states 
laws have been enacted regulating the manufacture 
and sale of commercial fertilizers, and provision is 
made for inspection and analysis of all brands offered 
for sale. The label on the fertilizer package must 
specify the percentage amounts of available nitrogen, 
phosphoric acid and potash. Inspection has been 
found necessary in order to protect the farmer and the 
honest manufacturer. As the result of inspection and 
analysis occasionally a fraud is revealed like the fol- 
lowing : 7^ 

Natural plant food, $25 to I28 per ton. 
Composition. Per cent. 

Total phosphoric acid 22.21 

Insoluble " " 20.8r 

Available " " 1.40 

Potash soluble in water 0.13 

Actual value per ton, $1.52. 

271. Mechanical Condition of Fertilizers. — When 
a fertilizer is purchased, its mechanical condition 
should be considered. The finer the fertilizer, as a 
rule, the better it is for promoting crop growth. 
Some combinations of plant food produce fertili- 
zers which become so hard and lumpy that it is diffi- 
cult to crush the lumps before spreading. The 
mass must be pulverized so that it may be evenly dis- 
tributed, otherwise the plant food will not be econom- 
ically used. - A fertilizer that passes through a sieve 
with holes 0.25 mm. in diameter is more valuable and 
can be used to better advantage than one of the same 
composition with particles 0.5 mm. in size. 

272. Forms of Nitrogen in Commercial Fertilizers, 



COMMERCIAI, FERTILIZERS 20I 

—Nitrogen is present in commercial fertilizers in 
three forms : (i) Ammonium salts, (2) nitrates, and 
(3) organic nitrogen. The organic nitrogen is divided 
into two classes : (a) available, and (d) unavailable. 
Pepsin and also potassiu mpermanganate are used as 
solvents for determining the availability of the organic 
nitrogen. The relative values of the different forms 
of nitrogen are discussed in Chapter IV. Three fer- 
tilizers may have the same amount of total nitrogen 
and still have entirely different crop-producing powers. 

No. I. No. 2. No. 3. 

Nitrogen as : Percent. Percent. Percent. 

Ammonium compounds 1.75 0.25 o. 10 

Nitrates. 0.15 0.15 0,10 

Organic nitrogen : 

Soluble in pepsin o. 10 1.25 0.55 

Insoluble in pepsin 0.35 1.25 



Total 2.00 2.00 



2.00 



In purchasing fertilizers it is important to know not 
only the amount of nitrogen, but also the form in 
which it is present. In No. 3 the nitrogen is in an 
inert form like leather, while in No. 2 it is largely in 
the form of dried blood, and No. i has mainly am- 
monium compounds. Each of these fertilizers, as ex- 
plained in the chapter on nitrogenous manures, has a 
different plant food value. 

273.. Phosphoric Acid. — There are three forms of 
phosphoric acid in commercial fertilizers : (i) Water 
soluble, (2) citrate-soluble, and (3) insoluble. The 
water and citrate-soluble are called the available phos- 
phoric acid. In most fertilizers the phosphoric acid 



202 SOILS AND FERTILIZERS 

is derived from dissolved phosphate rock, and is in the 
form of monocakium phosphate. The citrate-soluble 
is mainly dicalcium phosphate with variable amounts 
of iron and aluminum phosphates in easily soluble 
forms. The insoluble phosphoric acid is tricalcium 
and other phosphates which are soluble only in strong 
mineral acids. The insoluble phosphoric acid in fer- 
tilizers is considered as having but little value. As in 
the case of nitrogen three fertilizers may have the 
same total amount of phosphoric acid and yet have 
entirely different values. 

No. I. 
Per cent. 

Water-soluble phosphoric acid. 8.00 

Citrate-soluble " " 1.50 

Insoluble 0.50 

Total 10.00 10.00 10.00 

No. 3 is of but little value ; the fertilizer contains 
insoluble phosphate rock or some matarial of the same 
nature. No i is the most valuable, because it con- 
tains dissolved phosphate rock or dissolved bone and 
but little insoluble phosphoric acid. No. 2 is com- 
posed of such materials as the best grade of basic slag 
or roasted aluminum phosphate or fine steamed bone. 

274. Potash. — The three forms of potash in fer- 
tilizers are: (i) water-soluble, (2) acid-soluble, and (3) 
insoluble. Sulphate of potash, kainit, and muriate of 
potash, are soluble in water and belong to the first 
class. In some states the fertilizer laws recognize 
only the water-soluble potash. In the second class 
are found materials like tobacco stems and other 



No. 2. 
Per cent. 


No. 3. 
Per cent. 


0.25 


0.25 


8.00 


0.75 


1-75 


9.00 



COMMERCIAI. FERTILIZERS 203 

organic forms of potash. Substances like feldspar, 
which contain insoluble potash, are of no value in fer- 
tilizers. As a rule, the potash in commercial ferti- 
lizers is soluble in water ; in only a few cases are acid- 
soluble forms met with. Insoluble potash would be 
considered an adulterant. 

275. Misleading Statements on Fertilizer Pack- 
ages, — Occasionally the percentage amounts of nitro- 
gen, phosphoric acid, and potash are stated in mis- 
leading ways ; as ammonia, sulphate of potash, and 
bone phosphate of lime. Inasmuch as ammonia con- 
tains 14 parts nitrogen and three parts by weight of 
hydrogen, it follows that the ammonia content is pro- 
portionally greater than the nitrogen content, be- 
cause of the additional hydrogen carried by the ammo- 
nia. And so with sulphate of potash which contains 
about 50 per cent, potash and 50 per cent, of sulphuric 
anhydrid. This method of stating the composition 
can be considered in no other way than as a fraud, 
especially when the fertilizer contains no sulphate of 
potash, but cheaper materials, and the phosphoric acid 
is not derived from bone. 

276. Estimated Commercial Value of Fertilizers. 
— The estimated value of a commercial fertilizer is 
obtained from the percentage composition and the 
trade value of the materials used. Suppose that two 
fertilizers are selling at $25 and $30, respectively, 
each having a different composition, the estimated 
values of each would be obtained in the following 
way r 



204 



SOILS AND FERTILIZERS 



Composition of Fertilizers. 

No. I. 
Selling price $25. 
Per cent. 

Nitrogen as nitrates 1.50 

Phosphoric acid, available 8.00 

" " insoluble 2.00 

Potash (water-soluble) 2.00 

Pounds per Ton. 

No. I. 

Nitrogen 1.50X20= 30 

Phosphoric acid . . 8.0 X 20*= 160 
Potash 2.0 X2o= 40 

Estimated Value. 

No. I. 

Nitrogen 3° X o. 145 = 14-35 

Phosphoric acid 160 X o-o6 = 9.60 

Potash 40X0.045-= 1.80 



2.10 
lo.o 
3-5 



No. 2. 
Selling price $30. 
Per cent. 

2.10 

10.00 

0.50 

3-50 



No. 2. 
20 = 42 
20 = 200 
20= 70 



No. 2. 
42X0.145 = 16.09 



200 X 0.06 
70 X 0.045 



12.00 

3.15 



|r5-75 I21.24 

Difference between estimated value and selling 
price, No. i, $9.25; No. 2, $8.76. 




/ 2 

Fig. 34. Composition of Fertilizers. 

277. Home Mixing of Fertilizers. — At the New 

Jersey Experiment Station it has been shown that 
" the charges of the manufacturers and dealers for 
mixing, bagging, shipping, and other expenses are on 
the average $8.50 per ton, and also that the average 
manufactured fertilizer contains about 300 pounds of 



COMMERCIAIv FERTILIZERS 205 

actual fertilizing constituents per ton. These figures 
are practically true of other states where large quan- 
tities of commercial fertilizers are used."^^ In states 
where smaller amounts are used the difference between 
the estimated cost and selling price is greater than 
18. 50. 

These facts emphasize the economy of home mix- 
ing. The ^difference in price between the raw mate- 
rials and the product sold is frequently so great that 
it is an advantage for the farmer to purchase the raw 
materials, as sulphate of potash, nitrate of soda, and 

o 

bfiO 
a'-Z u 

Formula No. t. y B.-^ 

Pounds. Pounds, pi, 8^ 

Nitrate of soda 500 containing nitrogen 77.5 3.87 

Acid phosphate 1200 containing phos. acid... 168.0 8.40 

Sulphate of potash . . 300 containing potash 150.0 7.50 

Total 395.5 

F0RMUI.A No. 2. 

Nitrate of soda 250 containing nitrogen 38.7 1.99 

Acid phosphate 900 containing phos. acid- . . 126.0 6.3 

Sulphate of potash . . 450 containing potash 225.0 11.5 

Plaster, etc 400 

Total 389.7 

F0RMUI.A No. 3. 

Nitrate of soda 200 containing nitrogen 31.0 1.55 

Acid phosphate 1500 containing phos. acid. . . 210.0 10.50 

Sulphate of potash . . 150 containing potash 75.0 5.75 

Plaster, etc 150 

Total 316.0 



2o6 SOILS AND FERTILIZERS 

acid phosphate, and mix them as desired. By so 
doing a fertilizers of any composition may be pre- 
pared and there is less danger of securing an inferior 
article. Of course it is not possible by means of 
shovels and sieves to accomplish as thorough mixing 
of the ingredients as with machinery. 

278. Fertilizers and Tillage. — Commercial fer- 
tilizers cannot be made to take the place of good till- 
age, which is equally as important when fertilizers 
are used as when they are omitted. Scant crops are 
as frequently due to the want of proper tillage as to 
the absence of plant food. Poor cultivation results in 
getting the soil out of condition ; then instead of thor- 
ougly preparing the land, commercial fertilizers are 
resorted to, and the conclusion is reached that the soil 
is exhausted, when in reality it is suffering for the 
want of cultivation, for a dressing of land plaster, for 
farm manures, or for a change of crops. There is no 
question but what better tillage, better care and use 
of farm manures, the culture of clover and the sys- 
tematic rotation of crops would result in greatly re- 
ducing the amount annually spent for commercial 
fertilizers, and also increasing the yield of crops. The 
better the cultivation, the less the amount of commer- 
cial fertilizer required. Cultivation cannot, however, 
entirel}^ take the place of fertilizers. 

279. Abuse of Commercial Fertilizers. — When a 
soil produces poor crops, a complete fertilizer is fre- 
quently used when an amendment only is needed. 
Restricted crop production in long cultivated soils is 



COMMERCIAL FERTILIZERS 207 

usually due to deficiency of humus and available 
nitrogen. If the nitrogen were supplied, improved 
cultivation together with the chemical action of the 
humus on the soil would generally furnish the avail- 
able potash and phosphoric acid, but instead of pro- 
viding the one element needed, others which may 
already be present in the soil in liberal amounts, are 
often supplied at an unnecessary expense. Another 
abuse of fertilizers is their application to the wrong 
crop. A heavy application of potash fertilizer to a 
wheat crop grown on a clay soil, or an application of 
nitrate of soda on land seeded to clover, or of land 
plaster to flax grown on a limestone soil, would be 
a waste of money. 

280. Judicious Use of Fertilizers. — In order to 
make the best use of commercial fertilizers, both 
the soil and the crop must be carefully considered. 
All crops do not possess the same power of assimilat- 
ing food ; turnips, for example, have very restricted 
powers of phosphate assimilation, hence they require 
phosphate manures. Wheat requires help in obtain- 
ing its nitrogen. In some soils a wheat crop may 
starve for want of nitrogen, while an adjoining corn 
crop^ will scarcely feel its need. Wheat has strong 
power of assimilating potash, while clover has less. 
Hence in the use of fertilizers the power of the plant 
to obtain its food must be considered. A light appli- 
cation of either a special purpose or a complete fertili- 
zer at the time of seeding is often advantageous, as 
it encourages plant growth by supplying food at the 



2o8 SOILS AND FERTILIZERS 

time when it is most needed. There should be some 
plant food in the soil in a highly available condition 
for the use of young plants, after that stored up in the 
seed has been exhausted. Before commercial fertilizers 
are used, careful field trials should be made. 

281. Experimental Plots.— A piece of land well 
tilled and of uniform texture, should be used for field 
trials with fertilizers. After preparation for the crop, 
small plots, 1/20 of an acre, are staked off. A con- 
venient size is, length 204 feet, width 10 feet 8 inches, 
area 2176 square feet. Between each plot a strip 3 
feet wide is left. The plan is to apply one element 
or a combination of elements to a plot and compare 
the results with other plots treated differently. 7° 

282. Preliminary Trials. — It is best to make pre- 
liminary trials one year and verify the conclusions the 
next. In making the tests the first year eight plots 
are necessary and fertilizers are applied in the follow- 
ing way : 

The first plot receives no fertilizer and is used as 
the basis for comparison. 

The second plot receives a dressing of 8 pounds 
nitrate of soda, 16 pounds acid phosphate, and 8 
pounds sulphate or muriate of potash. 

The third plot receives nitrogen and phosphoric 
acid. 

The fourth plot receives nitrogen and potash. 
The fifth plot receives nitrogen. 



COMMERCIAL FERTILIZERS 



209 



The sixth plot receives phosphoric acid and potash, 

The seventh plot receives potash. 

The eighth plot receives phosphoric acid. 



No fertilizer. 
I. 


N 
P.O5 

2. 


N 
P2O5 

3- 


N 
4. 




N 
5- 


P2O5 
K,0 

6. 


K2O 

7. 


P2O5 
8. 



Should good results be obtained on plot No. 3, the 
indications are that there is a deficiency of the two 
elements nitrogen and phosphoric acid. An increased 
yield from No. 4 indicates deficiency of nitrogen and 
potash. Under such conditions the use of a complete 
fertilizer would be unnecessary. If No. 5 gives an 
additional yield the soil is in want of nitrogen. From 
the eight plots it will be possible to tell which of the 
various elements it is advisable to use. The fertilizers 
should be applied after the land has been thoroughly 
prepared and before seeding. Corn is a good crop for 
the first trials. The number of plots may be increased 
by using well-prepared stable manure and gypsum on 
plots 9 and 10 respectively. The second year the 
results should be verified. 

283. Deficiency of Nitrogen. — If the results indi- 
cate a deficiency of nitrogen, select two crops, one as 
wheat which is particularly benefited by dressings of 
nitrogen, and another as corn which has less difficulty 
in obtaining this element. The cultivation of each 



(14) 



2IO SOII.S AND FERTILIZERS 

crop should be that which experience has shown to 
be the best. . On one wheat, and one corn plot, 8 
pounds of nitrate of soda should be used, a plot each 
of wheat and corn being left unfertilized. If both the 
corn and the wheat are benefited by the application 
of nitrogen, the soil is in need of available nitrogen. 
If, however, the wheat responds and the corn does not, 
the soil is not in great need of nitrogen but does not 
contain an abundance in available forms. 

284. Deficiency of Phosphoric Acid. — In experi- 
menting with phosphoric acid, turnips are grown on 
two plots and barley on two plots. To one plot of 
each 16 pounds of acid phosphate are applied. If 
both crops show marked additional yields the soil is 
in need of available phorphoric acid. If only the 
turnips respond while the barley is indifferent, the soil 
contains a fair amount of available phosphoric acid. 
Barley and turnips are used because there is such a 
marked difference in the power of each to assimilate 
phosphoric acid. 

285. Deficiency of Potash, — In order to determine 
the condition of the soil as to potash, potatoes and 
oats may be used as the trial crops, and 8 pounds of 
sulphate of potash should be applied to one plot of each. 
Marked additional yields indicate a poverty of availa- 
ble potash ; an increased potato crop and an indiffer- 
ent oat crop indicate potash not in the most available 
forms. If no additional yields are obtained from 
either crop the soil is not in need of potash. 



COMMERCIAL FERTILIZERS 211 

286. Deficiency of Two Elements. — If the prelim- 
inary trials indicate a deficiency of two elements as 
nitrogen and phosphoric acid, in verifying these 
results, both elements are used together, in the same 
way as described for deficiency of nitrogen, with addi- 
tional plots for the separate application of nitrogen 
and phosphoric acid. 

287. Importance of Field Trials. — While it is a 
difficult matter to determine the actual needs of a 
soil, it will be found that both time and money are 
saved by a systematic study of the question. Suppose 
fertilizers are used in a "hit or miss" way year after 
year on a soil, deficient only in phosphoric acid. It 
might take 8 years to indicate what the soil really 
is deficient in if a different fertilizer is used each 
year, and during all this period, either the soil 
fails to receive its proper fertilizer, or expensive and 
unnecessary plant food is provided. Field tests to be 
of value must be continued for a number of years and 
the results verified. 

288. Will it Pay to Use Commercial Fertilizers? 

— This question can be answered only by trial. If a 
soil is in need of available plant food, the additional 
yield of crops should pay for the fertilizer and 
the expense of using it. Some fertilizers have an 
influence on two or three succeeding crops, and only 
partial returns are received the first year. When 
large crops must be produced on small areas, as in 
truck farming, commercial fertilizers are generally 
necessary. In the production of large areas of staple 



212 SOII.S AND FERTILIZERS 

crops as wheat and corn, in the western prairie states, 
they have not as yet been used. If there is a good 
stock of natural fertility, the soil is well tilled, farm 
manures are used, and crops systematically rotated, the 
use of commercial fertilizers can be avoided. With 
poor cultivation and a soil that has been impover- 
ished by injudicious cultivation their use is more 
necessary. Commercial fertilizers sometimes fail to 
give beneficial results, because of either an excessively 
acid or alkaline condition of the soil. 

289. Amount of Fertilizer to Use per Acre. — When 
commercial fertilizers are used, it should be the aim 
in general farming to apply just enough to produce 
normal yields. Heavy applications at long intervals 
are not as productive of good results as light applica- 
tions more frequently. From 400 to 600 pounds per 
acre is as much as should be used at one time unless 
previous trials have shown that heavier applications 
are necessary. The way in which the fertilizer is to 
be applied, as broadcast or otherwise, must be deter- 
mined by the crop to be grown. The fertilizer should 
not come in direct contact with seeds, neither should 
it be plowed under or worked into the soil to such a 
depth that it may be lost by leaching before it can be 
appropriated by the crop. 

290. Excessive Applications of Fertilizers Injuri- 
ous. — An overabundance of plant food has an inju- 
rious effect upon crop growth. Plants take their food 
from the soil in dilute solutions, and when the solu- 
tion is concentrated abnormal growth results. Pota- 



COMMEJRCIAL FERTILIZERS 213 

toes heavily manured with nitrate of soda make a 
luxuriant growth of vines but produce only a few 
small tubers. When a medium dressing is used along 
with potash and phosphoric acid, a more balanced 
growth is obtained, and a better yield is the result. . 

Heavy applications of nitrate of soda produce a rank 
growth of straw, with a low yield of grain. The ex- 
cessive amount of nitrogen causes the mineral matter 
to be utilized for straw production and leaves only a 
small amount for grain production. When applica- 
tions of commercial fertilizers aro too heavy, plants 
take up unnecessary amounts of food and fail to make 
good use of it. In fact crops may be overfed or fed, 
an unbalanced ration, the same as animals. Hence 
in the use of fertilizers excessive or unbalanced appli- 
cations are to be avoided. 

291. Fertilizing Special Crops. — There are crops 
which need special help in obtaining some one ele- 
ment, and in the use of fertilizers it should be the 
rule to help those crops which have the greatest diffi- 
culty in obtaining food. When the soil does not show 
a marked deficiency in any one element, light dress- 
ings of special purpose manures may be made to the 
following crops : 

Wheat. ^ — Nitrogen first, then phosphoric acid. 

Barley^ oats^ and rye require manuring like wheat, 
but to a less extent. Each crop has a different power 
of obtaining nitrogen. Wheat requires the most help 
and barley and rye the least. 



214 SOILS AND FERTILIZERS 

Ct>r7i. — Phosphoric acid first, then nitrogen and 
potash. 

Potatoes. — General manuring, re-enforced with pot- 
ash. 

'Mangels. — Nitrogen. 

Tiumips. — Phosphoric acid. 

Clover. — Lime and potash. 

Timothy. — General manuring. 

292. — Commercial Fertilizers and Farm Manures. 

— Commercial fertilizers should not replace farm 
manures, but simply re-enforce them. iVlthough 
commercial fertilizers are called complete manures, 
they fail to supply organic matter. It is more im- 
portant in some soils than in others, that the organic 
matter be maintained, because in some soils the 
organic matter takes a more important part in crop 
production than does the food applied in commercial 
forms. When a rich prairie soil is reduced by grain 
cropping and is allowed to return to pasture, heavier 
yields of grain are afterwards obtained than from sim- 
ilar soils which have received only applications of com- 
mercial fertilizers. This is due to the action of the 
humus in the soil. At the Canadian Dominion Ex- 
perimental farms where comparative trials have been 
made for fourteen years with farm manures and com- 
mercial fertilizers, it has been found that farm 
manures even on new lands give better results than 
commercial fertilizers for production of wheat and 
corn. 



CHAPTER XI 

FOOD REQUIREMENTS OF CROPS 

293. Amount of Fertility Removed by Crops.— 

From an acre of soil, producing average crops, the 
amount of fertility removed varies between wide lim- 
its. For example, an acre of mangels removes 150 
pounds of potash, while an acre of flax removes 27 
pounds ; an acre of corn removes about 75 pounds 
of nitrogen, while an acre of wheat removes 35 
pounds. Crops which remove the most fertility do 
not always require the most help in obtaining their 
food. This is because the amount of plant food 
assimilated is not a measure of the power of crops 
to obtain food. iVn acre of corn, for example, takes 
over twice as much nitrogen as an acre of wheat, but 
wheat will often leave the soil in a more impover- 
ished condition than corn, because corn has greater 
power for procuring nitrogen and for utilizing that 
formed by nitrification after the wheat crop has com- 
pleted its growth. The available nitrogen if not 
utilized by a crop may be lost in various ways. Man- 
gels require about twice as much phosphoric acid as 
flax, but are a strong feeding crop and require less 
help in obtaining this element. 

It was formerly believed that the plant food 
present in the matured crop indicated the kind 
and amount of fertilizing ingredients to apply, and 
that a correct system of manuring required a return 



2l6 SOILS AND FERTILIZERS 

to the soil of all elements removed in the crop. Ex- 
periments have shown that this view is incorrect. 
The composition of plants cannot be taken as the 
Pi^ANT Food Removkd by Crops^^ 

Pounds per acre. 
Phos- 
Gross Nitro- phoric Pot- Sil- Total 

Crops. weight. gen. acid. ash. Lime. ica. ash. 

Wheat, 20 bus 1200 25 12.5 7 i i 25 

Straw 2000 10 7.5 28 7 115 185 

Total 35 20 35 8 116 210 

Barley, 40 bus 1920 28 15 81 12 40 

Straw . 3000 12 5 30 8 60 176 

Total 40 20 38 9 72 216 

Oats, 50 bus 1600 35 12 10 1.5 15 55 

Straw r 3000 15 6 35 9.5 60 150 

Total 50 18 45 ii.o 75 205 

Corn, 65 bus 2200 40 18 15 i i 40 

Stalks 3000 35 2 45 II 89 160 

Total 75 20 60 12 90 200 

Peas, 30 bus 1800 .. 18 22 4 i 64 

Straw 3500 .. 7 38 71 9 176 

Total . . 25 60 75 10 240 

Mangels, 10 tons.. 20000 75 35 150 30 10 350 

Meadow hay, i ton 2000 30 20 45 12 50 175 
Red Clover Hay, 

2 tons 4000 . . 28 66 75 15 250 

Potatoes, 150 bus.. 9000 40 20 75 25 4 125 

Flax, 15 bus 900 39 15 8 3 o 5 34 

Straw 1800 15 3 19 13 3 53 

Total 54 18 27 16 3.5 87 

basis for their manuring. For example an acre of 
wheat contains 35 pounds of nitrogen while an acre 
of clover contains 70 pounds. If 70 pounds of nitro- 
gen were applied to an acre of clover and 35 pounds 
to an acre of wheat, poor results would follow, be- 
cause clover can obtain its own nitrogen while wheat 



FOOD REQUIREMENTS OF CROPS 21'] 

is nearly helpless in obtaining it, and the 35 pounds 
would not necessarily come in contact with the roots 
so that it could all be assimilated. While the amount 
of plant food removed in crops cannot serve as the 
basis for their manuring, valuable results are ob- 
tained from a study of the different elements of fer- 
tility removed in crops. In making use of the pre- 
ceding table, other factors, as the influence of the 
crop upon the soil and the power of the crop to ob- 
tain its food, must also be considered. 

294. Plants Exert a Solvent Power in Obtaining 
Food. — It was supposed at one time that plants ob- 
tained all of their mineral food from the mineral matter 
dissolved in the soil water. See Section 87. Experiments 
by lyiebig demonstrated that plants have the power of 
rendering a large portion of their own food soluble, 
provided it does not exist in forms too inert to under- 
go chemical change. Liebig grew barley in boxes so 
constructed that all of the water-soluble plant food 
could be secured. Two of the boxes were manured 
and two left unmanured. In one box which received 
manure and one which received none, barley was 
grown. One each of the manured and unmanured 
boxes was left barren. He collected all of the drain 
waters and determined the soluble mineral matter 
present, also weighed and analyzed the crops. His 
results s'howed that 92 per cent, of the potash in the 
crop was obtained from forms insoluble in water. 73 
Other experiments have shown that the leachings 
from a fertile soil do not contain sufficient plant food 
to grow a normal crop.^^ 



2l8 SOILS AND FERTILIZERS 

In the roots of all plants there are present various 
organic acids and salts. Between the rootlet and the 
soil there is a layer of water. The plant sap and the 
soil water are separated by plant tissue which serves as 
a membrane. All of the conditions are favorable for 
osmosis. The sap from the roots finds its way into 
the soil in exchange for some of the soil water. The 
acid and compounds, excreted by the roots, act upon 
the mineral matter, rendering portions of it soluble, 
when it is taken up by the plant. Different plants con- 
tain different kinds and amounts of solvents, as well 
as present different areas of root surface to act upon 
the soil, and the result is that agricultural crops have 
different powers of assimilating food. This action of 
living plant roots upon soils is a digestion process which 
is somewhat akin to the digestion of food by animals. 

Plants not only possess the power of rendering their 
food soluble but they are also able to select their food 
and to reject that which is unnecessary. For ex- 
ample, wheat grown on prairie soil containing soda in 
equally abundant and soluble forms as the potash, 
will contain relatively little soda compared with the 
potash. 37 

CEREAL CROPS 

295. General Food Requirements. — Cereal crops con- 
tain a high per cent, of silica and evidently possess 
the power of feeding upon some of the simpler silicates 
of the soil74 liberating the base elements and using 
them as food, while the silica is deposited in the 
outer surface of the straw. As previously stated, 



FERTILIZERS FOR CEREAL CROPS 219 

cereal crops, although they do not remove large 
amounts of total nitrogen from the soil, require 
special help in obtaining this element. There is, 
however, a great difference among the cereals as to 
power of assimilating nitrogen. Next to nitrogen 
these crops stand most in need of phosphoric acid. 
The humic phosphates are utilized by nearly all of 
the cereals. 

296. Wheat. — This crop is more exacting in its 
food requirements than barley, oats, or rye. Wheat 
is comparatively a weak feeding crop, and the soil 
should be in a higher state of fertility than for other 
grains. The extensive experiments of Lawes and 
Gilbert have given valuable information regarding 
the effects of manures on wheat. Their results are 
given in the following table : ^4 

Average YieIvD of Wheat per Acre. 

Bushels. 

No manure for 40 years 14 

Minerals alone for 32 years 15 j 

Nitrogen " " " " 23I 

Farmyard manure for 32 years 32f 

Minerals and nitrogen for 32 years^ 36^ 

324 

1 86 pounds of nitrogen as sodium nitrate. 

2 86 " " " " ammonium salts. 

The food requirements of wheat are such that it 
should, be given a favored position in the rotation. It 
may follow clover provided the clover sod is light 
and is fall plowed. On some soils, however, wheat 
does not thrive following a sod crop, as it takes nearly 
a year for a heavy sod residue to get into suitable food 



220 SOILS AND FERTILIZKRS 

forms for a wheat crop. Under such a condition, oats 
should first be sown, then wheat may follow. On 
average soil a medium clover sod, plowed late in 
summer or in early fall, and followed by surface cul- 
tivation, leaves the land in good condition for spring 
wheat. It is not advisable to have wheat follow bar- 
ley, because the soil will be too porous, and barley 
being a stronger feeding crop leaves the land in poor 
condition as to available plant food. When a corn 
crop is well manured, wheat may follow. The food 
requirements of wheat are best satisfied following 
a light, well cultivated clover sod, or following oats, 
which have been grown on heavy sod, or following 
corn that has been well manured. When wheat is 
judiciously grown in a rotation and farm manures are 
used it is not an exhausting crop. 

297. Barley. — While wheat and barley belong to 
the same general class of cereals, they differ greatly 
in their habits and food requirements. Barley is a 
stronger feeding crop, has greater root development 
near the surface, and can utilize food in cruder forms. 
In many of the western states, soils which produce 
poor wheat crops, from too long cultivation, give ex- 
cellent yields of barley. This is due to changed con- 
ditions, of both the chemical and mechanical composi- 
tion of the soil. Long cultivation has made the soil 
porous and reduced the nitrogen content. Barley 
thrives best on a rather open soil and has greater 
nitrogen assimilative powers than wheat. Barley, 
however, responds liberally to manuring, particularly 



FKRTILIZKRS FOR CERKAL CROPS 221 

to nitrogenous manures. The experiments of Lawes 
and Gilbert on the growth of barley are briefly sum- 
marized in the following table.^s 

Average Yiei,d of Bari^ey Per Acre for 34 Years. 

Bushels. 

No manure 1 7i 

Superphosphate alone 23I 

Mixed minerals 24^ 

Nitrogen alone 3o| 

Nitrogen and superphosphate 45 

Farmyard manures .... 491^ 

298. Oats.— Oats are capable of obtaining food un- 
der more adverse conditions than either barley or 
wheat. They are also less exacting as to the physical 
condition of the soil. The oat plant will adapt itself 
to either sandy or clay soil, and will thrive in the 
presence of alkaline matter or humic acid where 
wheat would be destroyed. In a rotation, oats usually 
occupy a position less favored by manures. Oats are, 
however, greatly benefited by fertilizers particularly 
by those of a nitrogenous nature. 

299. Corn. — Experiments with corn indicate that 
under ordinary conditions it requires most help in ob- 
taining phosphoric acid. Corn removes a large amount 
of gross fertility but its habits of growth are such that 
it generally leaves an average soil in better condition 
for succeeding crops. Corn is not injured as are many 
grain crops by heavy applications of stable manure. 
It does not, like flax, produce waste products which 
are destructive to itself. Rich prairie soils when 
newly broken give better results for wheat culture 



222 SOILS AND FERTILIZERS 

after one or two corn crops have been removed. The 
food requirements of corn are satisfied by applications 
of stable manure, occasionally re-enforced with a little 
nitrogen and phosphoric acid. After clover, corn gives 
excellent returns, and w^hen corn is the chief market 
crop it should be favored by having the best position 
in a rotation. . 

MISCELLANEOUS CROPS 

300. Flax is very exacting in food requirements 
and for its culture the soil must be in a high state of 
fertility. It is a type of weak feeding crop. There are 
but few roots near the surface and consequently it 
has restricted powers of nitrogen assimilation. 3^ Flax 
should be indirectly manured. Direct applications of 
stable manure produce poor results, but when the 
manure is applied to the preceding crop excellent re- 
sults are obtained. Flax does not remove a large 
amount of fertility, but if grown too frequently the 
tendency is to get the land out of condition rather 
than to exhaust it. The best conditions for flax cul- 
ture require that it should be grown on the same land 
only once in five years. Flax straw does not form 
suitable manure for flax lands. Dr. Lugger has 
demonstrated that there are produced, when the roots 
and straw of flax decay, products which are destruc- 
tive to succeeding flax crops. ^7 Flax diseases are also 
introduced into land by the use of diseased flax seed. 
The food requirements of flax are met when it follows 
corn which has been well manured, or a sod which 
has been o:iven the cultivation described for wheat. 



FERTILIZERS FOR ROOT CROPS 223 

Flax and spring wheat are much alike in food require- 
ments. 

301. Potatoes. — Potatoes are surface feeders and 
when grown continually upon the same soil without 
manure, the yield per acre decreases more rapidly than 
that of any other farm crop. Experiments with pota- 
toes by Lawes and Gilbert, using different manures, 
gave the following result i^^ 

Average Yiei.d Per Acre for 12 Years. 

Tons. Cwt. 

No manure i 1 9I 

Superphosphate 3 5 

Minerals alone 3 7l 

Nitrate of soda alone 2 4f 

Mixed manures and nitrogen 5 lyf 

Farm manures, alternate years 4 3I 

Potatoes require liberal general manuring re-enforced 
with wood ashes or other potash fertilizer. In the 
rotation they should follow grain or pasture land, pro- 
vided the fertility of the soil is kept up. 

302. Sugar-Beets. — This crop is more exacting in 
its food requirements than any other root crop. Ex- 
cessive fertility is not conducive to a high content of 
sugar. Soils in a medium state of fertility usually 
give the best results.79 Sugar-beets should not receive 
heavy dressings of stable manure, because an abnor- 
mal growth results. Nitrogenous fertilizers can be 
applied .only in limited amounts, heavier dressings of 
potash and phosphoric acid are more admissible. 
When sugar-beets follow corn which has been manured, 
or grain which has left the soil in an average state of 
fertility, the food requirements are well met. 



224 SOILS AND FERTILIZERS 

303. Roots. — Mangels are gross feeders and re- 
move a larger amount of fertility from the soil than 
any other farm crop.^^ When fed to stock and the 
manure is returned to the soil they materially aid in 
making the plant food more available for delicate 
feeding crops. Mangels are better able to obtain their 
phosphoric acid than are turnips and need the most 
help in the way of nitrogen. Turnips are surface 
feeders with stronger power of nitrogen assimilation 
than the grains, but with restricted power of phos- 
phate assimilation. Manures for turnips should be 
phosphatic in nature. 

304. Rape is a type of strong feeding plant capa- 
ble of obtaining its food under conditions adverse to 
grain crops. When grown too frequently upon the 
same soil it does not thrive. On account of its great 
capacity for obtaining food, it is a valuble crop to 
use for green manuring purposes. ^° 

305. Buckwheat is a strong feeding crop and its 
demands for food are easily met. On rich soil, a rank 
growth of straw results, with poor seed formation. 
Buckwheat is usually sown upon the poorest soil of 
the farm. Being a strong feeder it is used as a 
manurial crop, being plowed under while green to 
serve as food for weaker feeding crops. 

306. Cotton. — On average soils cotton stands in 
need first of phosphoric acid, second of nitrogen.^' It 
is most able to obtain potash. Organic nitrogen as 
cottonseed meal and stable manure appear equally 
as effective as nitric nitrogen. Phosphoric acid must 



FERTILIZERS FOR GRASS CROPS 225 

be applied in the most available forms. In fertilizing 
cotton, the use of green manuring crops as cow peas 
with an application of marl gives beneficial results. 
Marl, which is composed mainly of calcium carbonate, 
combines with the acids formed from the decay of 
this vegetable matter and as a result the plant food of 
the soil is more available, a result which is beneficial 
to both soil and crop. There are but few crops which 
respond so readily to fertilizers as cotton. 

307. Hops, — The hop plant is exacting in regard 
to its food requirements. An excess of easily soluble 
plant food is injurious while a lack is equally so. An 
abundance of food in organic forms is most essential. 
Heavy dressings of farm manures may be applied. 
Where hops are grown there is a tendency to use all 
of the manure on the hops while the rest of the farm 
is left unmanured. Very light applications of com- 
mercial fertilizers may be used in connection with 
stable manure, but such use should be made only 
after a preliminary trial on a small scale. 

308. Hay and Grass Crops. — Most grass crops have 
shorter roots than grain crops ; they are surface feed- 
ers and not so able to secure mineral food. When a 
number of crops have been removed the soil may stand 
in need of available mineral matter. Farm manures 
are particularly well adapted for fertilizing grass. Ap- 
plications of nitrogenous manures result in discourag- 
ing the growth of clover. Heavy manuring of grass 
land has a tendency to reduce the number of species 
and one kind is apt to predominate.^^ On some soils 

(15) 



226 SOILS AND FERTILIZERS 

ashes, and on others lime fertilizers, have been found 
very beneficial. The manuring of grass lands must 
be varied to meet the requirements of different soils. 
Permanent meadows require different manuring from 
meadow introduced as an important crop in the rota- 
tion. Permanent meadows should receive an annual 
dressing of farm manure or of a commercial fertilizer 
containing phosphoric acid, potash and a fair amount 
of nitrogen. 

309. Leguminous Crops. — For leguminous crops 
potash and lime fertilizers have been found of most 
value. Analyses of clover and peas, show large 
amounts of both potash and lime. Some crops 
as clover fail when grown too frequently upon 
the same soil, not because the soil is exhausted but be- 
cause of the development in the soil of organic pro- 
ducts which are destructive to growth. As the result 
of growing leguminous crops and after their inex- 
pensive food requirements are met, the soil is en- 
riched with nitrogen and the phosphoric acid is 
changed to available forms. 

310. Garden Crops. — For general garden purposes, 
there should be a liberal supply of plant food. Well 
composted farm manure can advantageously be rein- 
forced with commercial fertilizers. A liberal use of 
manures insures not only the maximum yield, but 
crops of the best quality. Maturity of crops also is 
influenced by fertilizers. 

Voorhees^9 recommends as a fertilizer for general gar- 
den purposes one containing : 



FERTILIZERS FOR GARDEN CROPS 227 

Per cent. 

Nitrogen 4.00 

Phosphoric acid 8.00 

Potash . 10.00 

This and similar fertilizers can be applied at the rate 
of 1000 pounds per acre. To meet the requirements 
of special crops, as spinach and cabbage, an additional 
dressing of nitrate of soda may be used. Asparagus 
should preferably be fertilized after harvesting the 
crop so as to encourage new growth and the storing 
up of reserved builing material in the roots for next 
year's growth. 

For early maturing garden crops, a fair but not 
excessive amount of nitrogen should be applied, 
also a more liberal supply of phosphates will be 
found advantageous. Some garden crops, as cu- 
cumbers, pumpkins and squash thrive best when 
their food is supplied in organic forms, as the humate 
compounds derived from farm manures. A continu- 
ous supply of available plant food is thus furnished to 
the growing crop. Onions are benefited by a gener- 
ous dressing of soluble nitrogen. Celery also should 
be well supplied with soluble nitrogen combined with 
soluble forms of mineral food. Tomatoes require 
general fertilizing ; for early maturity, nitrogen, as 
nitrate of soda, is beneficial, but an excess should be 
avoided ; for late maturity, farm manures and com- 
mercial fertilizers containing less nitrogen can be 
used. For general garden purposes, a complete fertili- 
zer is preferable to an amendment, as a better bal- 
anced growth is secured which favorably affects both 
thg yield and the quality of the crop. 



228 SOILS AND FERTILIZERS 

311. Fruit Trees. — In the manuring of fruit trees, it 
should be the object first to produce thrifty trees as sub- 
sequent fertilizing to produce fruit will not give satis- 
factory results with poorly grown and partially de- 
veloped trees. In order to promote growth, a liberal 
supply of a complete fertilizer should be used. When 
an orchard is in full bearing, there is as heavy a draft 
upon the soil as when a wheat crop is grown. 9° To 
meet this, farm manures and commercial fertilizers 
should be used liberally. The quality of the fruit is 
often adversely affected by a scant supply of plant 
food. A quick acting fertilizer containing kainit, 
nitrate of soda, and dissolved phosphate rock should 
be used in the spring, followed if necessary by a light 
dressing of some manure which yields up its fertility 
more slowly. Stone fruits are benefited by the addi- 
tion of lime to the fertilizer. 

312. Lawns, — In the preparation of a lawn, a 
mixture of six parts of bone ash, two parts of muriate 
of potash and one part of nitrate of soda can be ap- 
plied at the rate of 5 to 7 pounds per square rod prior 
to seeding. A good lawn should have a subsoil that 
is fairly retentive of moisture, one containing 10 to 
15 per cent, of clay or a large amount of fine silt. 
Too much potash and lime encourage exclusive growth 
of clover and crowding out of grasses. During the 
season, two or three applications can be made of a 
commercial fertilizer containing about 3 per cent, of 
nitrogen, 10 per cent, of phosphoric acid, and 3 per 
cent, of potash, at the rate of about one pound per 



MISCKI.I.ANKOUS CROPS 229 

square rod. When part of the nitrogen is in the form 
of nitrates and part as ammonium salts, better results 
are secured than when the nitrogen is all in one form. 
It is also advisable to supply the phosphoric acid in 
more than one form. An even application of fertili- 
zer to a lawn is quite necessary, otherwise the growth 
is "patchy." Hard wood ashes evenly spread at the 
rate of i to 2 pounds per square rod can also be used 
advantageously as a lawn fertilizer, and when used, 
they should be reinforced with nitrate of soda. 



CHAPTER XII 



ROTATION OF CROPS AND CONSERVATION OF SOIL 
FERTILITY 

313. Object of Crop Rotation. — The object of 
systematic rotation of crops is to conserve the fertility 
of the soil, and at the same time to produce larger 
yields. In order to accomplish this, the food require- 
ments of different crops must be met by good culti- 
vation and judicious manuring. Rotations must be 
planned according to the nature of the soil and the 
system of farming that is to be followed. For general 
grain farming a different rotation is required than for 
exclusive dairying. Whatever the nature of farming 
the whole farm should gradually undergo a systematic 
rotation. If the farm is uneven in soil texture, differ- 
ent rotations can be practiced on the various parts. 
There is no way in which soils are more rapidly de- 
pleted of fertility than by the continued culture of one 
crop. In exclusive wheat raising, for example, the 
losses which occur are not confined to the fertility re- 
moved in the crop but there are other losses as described 
in the chapter on nitrogen. When wheat is system- 
atically grown in alternation with other crops, losses 
of nitrogen are reduced to a minimum. 

When remunerative crops can no longer be produced 
the soil is said to be exhausted. Soil exhaustion may 
be due either to a lack of fertility or to the soil being 
temporarily out of condition because of a one-crop 
system and poor methods of cultivation. 



ROTATION OF CROPS 23 1 

314. Principles Involved in Crop Rotation, — In 

the systematic rotation of crops there are a few funda- 
mental principles with which all rotations should con- 
form. Briefly stated these principles are : 

1. Deep and shallow rooted crops should alternate. 

2. Humus-consuming and humus-producing crops 
should alternate. 

3. Crops should be rotated so as to make the best 
use of the preceding crop residue. 

4. Crops should be rotated so as to secure nitrogen 
indirectly from atmospheric sources. 

5. Crops should be rotated so as to keep the soil in 
the best mechanical condition. 

6. In arid regions crops should be rotated so as to 
make the best use of the soil water. 

7. An even distribution of farm labor should be se- 
cured by a rotation. 

8. Farm manures and fertilizers should be used in 
the rotation where they will do the most good. 

9. Rotations should be planned so as to produce 
fodder for stock, and so that every year there will be 
some important crop to be sold. 

315. Deep and Shallow Rooted Crops. — When 
deep and shallow rooted crops alternate, the draft upon 
the surface soil and subsoil is more evenly distributed. 
In many. soils nitrogen and phosphoric acid are more 
abundant in the surface soil while potash and lime 
predominate in the subsoil. When such a condition 
exists, the alternating of deep and shallow rooted 
crops is very beneficial, because the surface soil is re- 



232 SOILS AND FERTILIZERS 

lieved of continuous heavy drafts upon the elements 
present in scant amounts. 

316, Humus-consuming and Humus-producing 
Crops. — When grain or hoed crops are grown con- 
tinually, oxidation of the humus occurs, and the 
chemical and physical properties of the soil may be 
entirely changed by the loss of the humus. The ro- 
tating of grass and grain crops and the use of stable 
manure serve to maintain the humus equilibrium. On 
some soils lime may be required along with the humus 
to prevent the formation of humic acid, and in such 
cases the best conditions exist when both lime and hu- 
mus materials are supplied. The alternation of hu- 
mus-producing and humus-consuming crops is one of 
the essential matters to consider in a rotation. 

317. Crop Residues. — Crop residues should always 
be placed at the disposal of weak feeding crops. For 
example, after a light clover and timothy sod, wheat 
or flax should be grown in preference to barley or 
mangels. The weak feeding crop should then be fol- 
lowed by a strong feeding crop, and each is properly 
supplied with food. It would be poor economy, on an 
average vSoil, to follow clover and timothy with mangels, 
then with barley, and finally with flax, because the 
flax would be placed at a serious disadvantage follow- 
ing two strong feeding crops. If reversed, the crops 
would be placed in order of assimilative power, and the 
best use would be made of the sod crop residue. 
When crops of dissimilar feeding habits follow each 
other in rotation not only are the crop residues used to 



ROTATION OF CROPS 233 

the best advantage, but the soil is relieved of excessive 
demands on special elements. For example, wheat 
and clover take different amounts of potash and lime 
from the soil. Wheat has the power of feeding upon 
silicates of potash which clover cannot assimilate, 
hence wheat and clover in rotation relieve the soil of 
excessive demands on the potash. 

318. Nitrogen-consuming and Nitrogen-producing 
Crops. — It is possible in a five-course rotation to main- 
tain or even increase the nitrogen of the soil without 
the use of nitrogenous manures. In Section 134 an 
example is given of a rotation which has left the soil 
with a better supply of nitrogen than at the begin- 
ning. When a soil produces a good clover crop once 
in five years, and stable manure is used once during 
the rotation, the soil nitrogen is not decreased. By 
means of rotating nitrogen-producing and nitrogen- 
consuming crops grain can be sold from the farm 
without purchasing nitrogenous manures. The con- 
servation of the nitrogen and the humus of the soil 
is one of the most important points to consider in 
the rotation of crops. 

319. Influence of Rotation upon the Mechanical 
Condition of Soils. — With different kinds of crops, 
the mechanical condition of soils is constantly under- 
going change. Grain crops and hoed crops tend to 
make the soil open in texture. Grass crops have the 
opposite effect. All soils should undergo periodic 
compacting and loosening. Some require more of one 
treatment than of the other. In a rotation the 



234 SOILS AND FERTILIZERS 

action of the crop upon the mechanical condition of 
the soil should be considered, otherwise the soil may 
get into poor condition to retain water or become so 
loose that heavy losses occur through wind storms. 
Sandy soils are improved by those methods of cropping 
which compact the soil, while heavy clays require the 
opposite treatment. The rotation should be made to 
conform to the requirements of the soil. 

320. Economic Use of Soil Water. — The rotation 
should not be of such a nature as to make excessive 
demands upon the soil water. For example, after a 
grain crop has been produced, it is best in regions of 
scant rainfall to plow the land and get it into condi- 
tion to conserve the water for the next year's crop, 
rather than to attempt to raise a catch crop the same 
year. During years of heavy rainfall catch crops can 
be grown as green manure to increase the humus con- 
tent of the soil. Crops removing excessive amounts 
of water should not be grown too frequently. Sun- 
flowers, for example, remove twenty times more water 
than grain crops. Cabbage removes from the soil 
more water than many other crops. With a good 
rotation and systematic cultivation it is possible to 
carry a water balance in the soil from one year to the 
next, so that crops wall be supplied in times of drought. 

321. Rotation and Farm Labor. — The rotation of 
crops should be planned so that an even distribution 
of farm labor is secured. The importance of this 
is so plain that its discussion is unnecessary. It is 
one of the most important points to consider in 



ROTATION OF CROPS 235 

economic farming, and should not be lost sight of in 
planning rotations. 

322, Economic Use of Manures. — Farm manure 
should be applied to those crops which experience has 
shown to be the most benefited by its use. At least 
once during a five years' rotation the land should receive 
a dressing of stable or some other manure. If com- 
mercial fertilizers are used, they should be applied to 
the crops which require the most help in obtaining 
food. With the growing of clover and the use of 
farm manures, only the poorer kinds of soil will re- 
quire commercial fertilizers for general crop produc- 
tion. It is more economical to reenforce the farm 
manures with fertilizers especially adapted to the soil 
and crop, than to purchase complete fertilizers for all 
crops. 

323. Salable Crops. — In all farming, something 
must be sold from the farm. It should be the aim to 
sell products which remove the least fertility, or if 
those are sold which remove large amounts, to return 
in cheaper forms the fertility sold. In a good rotation 
it is the plan to have at least one salable crop each 
year. The whole farm need not undergo the same 
rotation at the same time and the rotation may be 
subject to minor changes as circumstances require. 
To illustrate, wheat and flax occupy about the same 
position in a rotation. If at seeding time the indica- 
tions are that wheat will be a poor paying crop and 
flax command a high price, flax should be sown. 
The rotation should be such that one of two or three 
crops may be grown as circumstances require. 



236 SOILS AND FERTILIZERS 

324. Rotation Advantageous in Other Ways. — 

A good rotation will be found advantageous in other 
ways. With one line of cropping, land becomes 
foul with weeds and insects which are unable to 
thrive when crops are rotated. Frequently the rota- 
tion must be planned so as to reclaim the land from 
weeds, and ravages caused by insect pests. Many in- 
sects are capable of living only on a special crop ; 
when this crop is grown continually on the same land 
the best conditions for insect ravages exist, and relief 
is only secured by rotation of crops. Fungus diseases 
also are most liable to occur on soils which produce 
annually the same crop, as the conditions are favorable 
for the propagation and hybernating of disease pro- 
ducing spores. 

325. Long- and Short- Course Rotations. — Rota- 
tions vary in length from 2 to 1 7 years. Long-course 
rotations are more generally followed in European 
and other of the older countries. The length of the 
rotation can only be determined by the conditions ex- 
cisting in different localities. As a general rule long- 
course rotations should be attempted only after a 
careful study of all of the conditions relating to the 
system of farming that it is desired to follow. For 
northern latitudes a rotation of four or five years 
gives excellent results. In some localities three- 
course rotations are the most desirable. 

A rotation that is suitable for one locality or kind 
of farming may be unsuitable for other localities or 
conditions. Because of variations in soil, climate, 



ROTATION OF CROPS 237 

and rainfall, no definite standard rotation can be pro- 
posed that will be applicable to all conditions. 

326. Example of Rotation. — In dealing with the 
subject of rotations it is best to take actual problems 
as they present themselves and plan rotations that 
will best meet all of the conditions. For example, a 
farm of i6o acres is to be rotated with the main ob- 
ject of producing fodder for live stock, and a small 
amount of grain for sale. To meet these require- 
ments the rotation outlined on pages 238 and 240 is 
given. ^3 

The farm is divided into eight fields of 20 acres 
each ; seven fields are brought under the rotation, 
while one field is left free for miscellaneous purposes. 
Each year there are produced 20 acres of corn, 20 
acres of timothy and clover hay, 10 acres each of 
wheat and flax, 20 acres of barley, and five acres each 
of corn fodder, rye, peas, and potatoes, while 20 acres 
are reserved for pasture. The main income is de- 
rived from the sale of live stock and dairy products. 





6 












6 














oT oj 1) t< 




S 

§ 

1- 






4J 




















potatoe 
peas, on 
e, on 
1 fodde 


^ 












^ 
^^■ 














.1^1 




o 


0) 


03 

s 

o 






03 






^ 








l|ll 




15 


CO 


03 












CO 








0) g 




o 


P; 


o 






O 






W 



















i 












en 


5" 


- 1 













a 















u 


>.o 


S 










o 












3 


3 



u 


(+1 





























Vi 


Td 








n3 


CC 












a 


OJ 







3 








(U 


lU 














c 





03 








S3 
















0_ 


^ 


^ 


th 


^ 


di 


S 


03 










5 

3 


1 


c 



3 


> 






O 




fl 


^ 






1^ 






a 


■d 




0) ^; 


^ >^ 




ci3 




(U 


rt 




CC 






iJ 






c <u 


i2 P 




ii 


rt 


o 


c 


^ 










S 


aond 




S 


p: 


o 


o 






PQ 
























a; 








cfi'-C 


a;rrt 


1 

















o 








03 O^ C 


B 
















1 








as 


1 


s 


G 
03 














3 













JH 


)h 










N 




n 




^ 

^ 






5-2 

•2; 


§ 

CO 


3 

a 

<V U 


> 




>^ 











to 
03 


^^ 


o3 






a 03 


4J 3 H 


03 

03 








03 
1^ 




p^ 


u 


O 


« 


























ij 




af 


"i" 


i 


• 6 




















O 




O 


§ 





^ B 


















f 

3 


-4-r 




o3 tn 

as. 


rye, 
rn fodc 
rand t 
















• 


c 


^ 


«■ ^ 


^ 


u, 




a; 
























il 3 3 ^ 1^ 




^ 

^ 








2i 

3 




o 




s s 


0) 


3 



a 


^^ 

«+H 03 +^ 














"S 

03 




U 


O 


a 


O 



















Ph 




03 


u 


;_, 


v^ 






u 






;h 








;h 




?, 


rt 


CO 






a 






03 








03 




a> 


S 


<v 






<v 






OJ 








<U 




>. 


>^ 


>^ 




>-, 






;>> 








>> 






•^ 


TS 


X 






Si 






J 








^ 




tn 


a 


Ui 














-M 












M 


cs 


rO 


Tj- 




"to 






VO 








t^ 



•vj 




ON 


C/i 


■^ 






Oi 








K> 






M 


rt- 






. p* 








'^ 








B 






en 


13* 




s* 


B* 


B* 






C^ 














1 

•-t 




(T) 




P3 






^ 
^ 








1 






rt 
P 
•-f 


o 




y 


(T) 
O 


O 






'^" 








?^ 






o 


3 

P 




03 


B 
g' 


B*^ O 

So o 

fD B B 


B 

B 

B' 

O 

P 








P 
•-t 

1 






p rt 
S^B* 
B^gL 

^« 
1 

O 

B 










9 


>-t 


1 1 


tn 














rt 

1 


o 




Q 


!;? 


rD 






O 








O 






W 


g-? 




o 


& 




§ 


P 
en" 


0^ 


Ml 

o 


o 

B 


B 
rD 






P 
•-t 








1 




^ 


O 


B 

B* 


B 


rD M, 

B* 






rD* 






B 

B 










re 
•-t 


8 
•-t 


B- 






p 

B 


0) 




1 










P 

B 


B 


rD 
P 

03 




1 

s 

o 

(X) 






B 
rt 

CI" 


o 














B 


rD 


o 


O 

B 








? 














o 


j-t 


1 


rc 


\n 








w 




o 


o 


nj 






k 

rt) 








~o~ 






o 


95 


B-B 


o 


en 










'^ ^ 


o- 


^o B 1 




P 




B 








p 








en 


o 


B '," 




P^^B* 








CI. 
o 






-^ 




B 


B 


2,^ 

5- S* 


g 




B 

B 


ft 






^ 








rD 


8 


B" 


o 




tr 
















■t 


'T3 
rt 
P 

jn 


B* 


1 






I 
















p 

B 
Cii 


o- 


- P 
B S 






o 

B 


















1 


rt 


O 
B 






? 


















O 


^ 


?. 


?« 














^ 




























sra 






























^ n 


fD 




























B o 


^ 




























S-B 






















, 








Pj 


a 






























•t 




























►a 


3 




























en 


S' 




























P 


H 




























B 


^ 




























O^f 



















240 SOILS AND FERTILIZERS 

Problems on Rotations 

1. Plan a rotation for general farming (160 acres) using the 
following crops: clover, timothy, barley, oats, potatoes, and corn. 
The soil is in an average state of fertility. Twenty-five head of 
stock are kept. 

2. Plan a three-course rotation for a sandy soil, the main ob- 
ject being potato culture. 

3. Plan a seven-year rotation for grain farming, using manure 
and a commercial fertilizer once during the rotation. The soil is 
a clay loam in a good state of fertility. 

4. Plan a rotation for general farming on a sandy loam. 

5. How would you proceed to bring an old grain farm from a 
low to a high state of productiveness ? Begin with the feeding of 
the stock. 

6. Using commercial and special purpose manures, how would 
you proceed to raise wheat, potatoes, and hay, in rotation and con- 
tinually ? 

7. Plan a rotation for a northern latitude, where corn cannot 
be grown, except for fodder, and where clover and timothy fail to 
do well ; wheat and all small grains thrive, also millet, bromus 
inermis, rape, and some of the root crops. The soil is a clay loam, 
resting on a marl subsoil. Manure is very slow in decomposing. 
The rotation should be suited to general farming, wheat or flax 
being the important market crop. 

8. Plan for a southern farm a rotation in which cotton forms 
an important part. 



CONSERVATION OF FERTILITY 

327. Manures Necessary for Conservation of Fer- 
tility. — In order to conserve the fertility of the soil, 
not only must a systematic rotation be practiced, but 
a proper use must be made of the crops produced. 
When crops are sold from the farm and no restoration 
is maed, soils are gradually depleted of their fertility. 
No soil has ever been found that will continue to pro- 
duce crops without the use of manures. Many prairie 
soils give large yields for long periods without manur- 
ing, but they are never able to compete in productive- 
ness with similar soils that have been systematically 
cropped and manured. With a fertile soil the decline 
of fertility is so gradual that it is not observed unless 
careful records are kept of the yields from year to year. 

328, Use of Crops. — The use made of crops whether 
as food for stock or sold directly from the farm, deter- 
mines the future crop-producing power of the soil. 
With different systems of farming different uses are 
made -of crops. When exclusive grain farming is fol- 
lowed no restoration of fertility is made, while in the 
case of stock farming, the manure produced contains 
fertility in proportion to the food consumed. If good 
care is taken of the manure, and in place of the grains 
sold, mill products are purchased and fed, there is no 
loss and often a gain of fertility. Between these two 
extremes, exclusive grain farming and stock farming, 
many different systems of farming are practiced which 
remove from the soil various amounts of fertility. 

(16) 



242 SOILS AND FKRTII.IZKRS 

329. Two Systems of Farming Compared. — The 

losses of fertility from farms are determined by the 
crops and products sold, the care of the manure, and 
the fertility in the products purchased and used on the 
farm. If an account were kept of the income and 
outgo of the fertility of farms, it would be found that 
with some systems the soil is gaining in fertility, while 
with others a rapid decline is occuring. In studying 
the income and outgo of fertility, it is necessary to 
calculate the amounts of the three principal elements, 
nitrogen, phosphoric acid, and potash in the crops and 
products sold. For making these calculations tables 
are given in Sections 172 and 293. In the handling 
of manure it is impossible to prevent losses, but it is 
possible to reduce them to very small amounts. 
Hence in the calculations, a loss of 3 per cent, is al- 
lowed for mechanical waste, and for uneven distribu- 
tion of the manure ; that is, in addition to the fertility 
sold from the farm a mechanical loss of 3 per cent, is 
allowed for all crops raised and consumed as food by 
stock. 

On one farm the crops raised and sold are : Flax 40 
acres, wheat 50 acres, oats 20 acres, barley 50 acres ; 
no stock is kept, the straw is burned, and the ashes 
are wasted. 

In addition to the nitrogen removed in the crops 
other losses must be considered. Experiments have 
shown that when exclusive grain farming is practiced, 
for every pound of nitrogen removed in the crop, four 
pounds are lost from the soil in other ways. See 



CONSERVATION OF FERTILITY 243 

section 133. This would make the total loss of nit- 
rogen over 28,500 pounds or 177 pounds per acre, 
which large as it may seem is the actual loss from 
the soil when grain only is raised and is sold. Ex- 
periments at the Minnesota Experiment Station 
showed that after a soil had been cultivated 40 years, 
the annual loss per acre of nitrogen in exclusive 
wheat raising was 25 pounds through the crop and 
146 pounds due to the oxidation of the nitrogenous 
humus of the soil.^^ 

Exclusive Grain Farjming. 

Sold from the Farm. 

Phosphoric 

Nitrogen. acid. Potash. 

Pounds. Pounds. Pounds. 

Flax, 40 acres 1600 600 800 

Flax straw 600 120 320 

Wheat, 50 acres 1250 625 350 

Wheat straw 500 375 1400 

Oats, 20 acres 700 240 200 

Oat straw 300 1 20 700 

Barley, 50 acres 1400 750 400 

Barley straw 600 250 1500 

Total 6950 3080 5670 

When exclusive grain farming is followed, the 
annual losses of fertility from a farm of 160 acres are 
28,500 pounds of nitrogen, 3000 pounds of phosphoric 
acid, and 5500 pounds of potash. 

On a similar farm of 160 acres the crops are rotated 
as described in Section 326. The amounts of fertility 
in the products sold, the crops raised and consumed 
as fodder, and the food and fuel purchased, are given 
in the following table. 



244 



SOILS AND FERTILIZERS 



Stock Farming. 
Sold from the Farm. 

Phosphoric 

Nitrogen. acid. Potash. 

Pounds. Pounds. Pounds. 

Butter, 5000 pounds 5 5 5 

Young cattle, 10 head 200 190 16 

Hogs, 20 of 250 pounds each . . 100 40 10 

Steers, 2 48 38 4 

Wheat, 10 acres 250 125 70 

Flax, 10 acres 390 150 190 

Rye, 10 acres 285 128 85 

Total 1278 676 380 

Raised and Consumed 07i the Farm. 

Clover, 20 tons 00 270 600 

Timothy, 20 tons 600 180 800 

Corn, 20 acres 1500 300 800 

Corn fodder, i acre 75 15 60 

Mangels, 2 acres 150 70 300 

Potatoes, I acre 40 20 75 

Straw, 40 tons 400 200 1000 

Peas, 5 acres 85 200 

Oats, 20 acres 700 240 200 

Barley, 20 acres with straw • • 800 400 760 

4265 1780 4795 
Mechanical loss of food con- 
sumed, 3 per cent 128 53 144 

Food a7id Fuel Purchased. 

Phosphoric 

Nitrogen. acid. Potash 

Pounds. Pounds. Pounds. 

Bran, 5 tons 275 260 150 

Shorts, 5 tons 250 150 100 

Oil meal, ton 100 35 25 

Hard-wood ashes 25 100 



625 



470 



375 



CONSERVATION OF FERTIUTY 245 

Mechanical loss in material 

purchased 3% 19 14 10 

Sold from farm 1278 676 380 

Loss in food consumed, etc 128 53 144 

Total 1425 743 534 

Food and fuel purchased .... 625 470 375 

Balance lost from farm 800 273 159 

The manure produced and used on this farm results 
in the production of larger crop yields than is the 
case with exclusive grain culture. The nitrogen 
gained by the clover and peas more than balances the 
loss of nitrogen in other crops. Experiments have 
shown that a rotation similar to this caused an in- 
crease in soil nitrogen.'^ Manure, meadow and past- 
ure all tend to increase the soil's humus and nitrogen. 
The losses of phosphoric acid and potash are exceed- 
ingly small, averaging about a pound per acre for 
each. The action of the manure on this farm is con- 
tinually bringing into activity the inert plant food 
of the soil so that every year there is a larger amount 
.of more active plant food, which results in producing 
larger yields per acre. 

The method of farming has a marked effect upon 
crop yields. The average yield of wheat in those 
counties in Minnesota where live stock is kept and 
crops are rotated, is over lo bushels per acre greater 
than in similar counties where exclusive grain farm- 
ing is followed. 



246 SOILS AND FERTILIZERS 

Problems. 

Calculate the income and outgo of fertility from the following 
farms. 

T. Sold from the farm : Wheat 40 acres, oats 40 acres, barley 40 
acres, rye 20 acres, flax 10 acres. The straw is burned and no use 
is made of any manures. 

2. Sold from the farm : Wheat 20 acres, barley 20 acres, flax 5 
acres, 1000 pounds of butter, 10 hogs, and 10 steers. Purchased : 
Bran 3 tons, shorts 2 tons, oil meal i ton. Crops produced and fed 
on farm : Clover and timothy hay 40 tons, corn fodder 3 acres, 
corn 10 acres, oats and peas -10 acres, roots i acre, millet i acre, 
and barley 5 acres. 

3. Sold from the farm : Wheat 10 acres, sugar beets 5 acres, 
milk 100,000 pounds, butter 500 pounds, 20 pigs, 6 head of young 
tock, 2 acres of potatoes. Purchased : 5 tons of bran, 2 tons of 
oil meal, i ton of cottonseed meal, 15 cords of wood, i ton of acid 
phosphate, 1000 pounds of potassium sulphate, and 500 pounds of 
sodium nitrate. Raised and consumed on the farm : Corn fodder 
15 acres, mangels i acre, peas and oats 5 acres, clover 20 tons, 
timothy 10 tons, straw from grain sold, oats 10 acres, corn 20 
acres. 

4. Calculate the income and outgo of fertility from your own 
farm. 



CHAPTER XIII 



PREPARATION OF SOILS FOR CROPS 

330. Importance of Good Physical Condition of 
Seed Bed. — But few soils are in suitable condition 
for seeding without farther preparation than simply 
plowing the land. If the plowing is poorly done, a 
good seed bed cannot be prepared. The depth of 
plowing is of prime importance and is determined 
largely by the character of the soil, as sand, clay or 
loam. (See Section 35). The character of the seed 
bed is influenced not only by the depth of plowing but 
by the nature of the plowing as the way in which the 
furrow slice is left. Treatment of the soil after plow- 
ing, as disking, harrowing, cultivating and light roll- 
ing must be determined largely from the character of 
the soil. Too frequently the preparation of the soil 
is not given sufficient attention and crops suffer be- 
cause of poorly prepared seed beds. 

331. Influence of Methods of Plowing Upon the 
Condition of the Seed Bed. — A poor seed bed is some- 
times formed by complete inversion of the furrow slice 
and the soil not being sufficiently pulverized. If a 
heavy sod has simply been inverted, subsequent harrow- 
ing and cultivation will fail to pulverize and loosen 
the tough sod in the lower part of the furrow slice. 



248 



SOII.S AND FERTII.IZKRS 



A good seed bed cannot be made upon such a foun- 
dation. When the land is plowed so that the furrow 
slice is left at an angle of 30 to 45 degrees, the surface 
is corrugated and all vegetation is buried in loose soil. 
When land which has been plowed in this way is culti- 
vated and harrowed, a better seed bed is formed than 
is possible on a completely inverted furrow slice. 




Fig. 35. A poor way of plowing sod laud (after Roberts). 




Fig. 36. Plowed land left in good condition for formation of seed 
bed (after Roberts). 

In plowing, it should be the aim to thoroughly pul- 
verize the soil, completely bury all surface vegetation, 
and leave the land in a corrugated condition with the 
furrow slice at an angle but firmly connected with the 
subsoil. The plowing should cause as thorough dis- 
integration of the soil as possible and this can best be 
accomplished by the use of a plow with a bold rather 
than too flat a moldboard. Roberts^^ states that only 
about 10 per cent, of the energy required for plowing 
is used by the friction of the moldboard: " About 35 
per cent, of the power necessary to plow is used by the 
friction due to the weight of the plow, and 55 per 
cent, by severing the furrow slice and the friction of 



PREPARATION OF SOILS FOR CROPS 249 

the land slide." In the preparation of the seed 
bed, it is economy to secure as much pulverization of 
the soil by the action of the plow as possible rather 
than to leave too much for subsequent treatment. 

332. Influence of Moisture Content of the Soil at 
the Time of Plowing. — The condition of the soil, 
particularly as to moisture content at the time of plow- 
ing, has much to do with the production of a good seed 
bed. If soils are too dry when plowed they fail to 
pulverize, and disking, harrowing, and in some cases 
light rolling, making additional expense, must be re- 
sorted to in order to produce a fine, mediumly compact 
and well pulverized seed bed. If clay soils are plowed 
when too wet, the pores of the subsoil become clogged, 
a condition known as puddling takes place, and the 
furrow slice dries and forms hard lumps and clods. 
The condition in which the soil is left after plowing, 
particularly in the case of clay soils, has much to do 
with the character of the seed bed and the subsequent 
yield of crops. 

333. Influence Upon the Seed Bed of Pulverizing 
and Fining the Soil. — If a soil is lumpy, and the 
lower strata of the seed bed is not pulverized and 
firmed, the soil readily loses water by percolation, 
evaporation takes place rapidly and the crops are 
poorly fed because the roots are unable to penetrate 
the hard lumps and secure plant food. If a soil is in- 
clined to be lumpy, the cultivation including the plow- 
ing should be carried on largely with the view of 
thoroughly pulverizing the soil. When a seed bed is 



250 SOILS AND FERTILIZERS 

well prepared, the soil warms up more readily. The 
loosening and pulverizing of the land enables the heat 
from the sun's rays to more readily penetrate the soil 
and bring the land into good condition for promoting 
growth. 

334. Aeration of Seed Bed Necessary. — Air is 
required for functional purposes by the roots of crops» 
In sand and loam the air spaces make up a half or more 
of the total volume. With such soils it is not neces- 
sary to cultivate with the view of increasing the air 
spaces, but in compact soils, as heavy clays, plowing 
should result in aeration of the soil and an increase in 
the number of air spaces, as the air of the soil takes an 
important part in rendering plant food available. (See 
Section 53). If soils are plowed when too wet they 
are not sufficiently aerated. The amount and kind of 
cultivation to secure the ventilation and aeration neces- 
sary for crop production must be regulated according 
to the character of the soil as sand, clay or loam, and the 
climatic conditions. The cultivation which is given 
soils for purposes of conservation of the moisture also 
secures the proper aeration. 

335. Preparation of Seed Bed Without Plowing. 

— Loam soils which have been subjected to a sys- 
tematic rotation of crops and upon which corn has been 
grown, need not be plowed but the seed bed for the 
succeeding grain crop can be prepared simply by disk- 
ing. Surface tillage of the corn crop has sufficiently 
loosened and aerated the soil and has caused an accu- 
mulation of available plant food near the surface which 



PREPARATION OF SOILS FOR CROPS 25 1 

would be buried and be less available to the crop if 
the land were plowed too deeply. On heavy clay 
lands this method of preparing the seed bed without 
plowing is not advisable but on the silt soils of the 
northwest it is a practice which has given excellent 
results and is beneficial as a means of conserving the 
soil moisture. 

336. Mixing of Sub-Soil With Seed Bed. — Some 
soils are improved by deep plowing and by mixing 
the surface soil and sub-soil to form the seed bed. Such 
soils are usually acid in character and contain a large 
amount of organic matter, in which case the mixing 
of the surface soil and subsoil improves both the physi- 
cal and chemical properties of the seed bed. In the 
case of sandy soils, the mixing of the surface soil with 
the sub-soil is not advantageous as it dilutes the stores 
of plant food which are greater in the surface soil ; 
then too the physical properties of the soil are not im- 
proved. The combining of the surface soil and sub- 
soil in the case of heavy clay should be done gradu- 
ally and at each period in the rotation after an appli- 
cation of farm manure. In the cultivation of clay 
soils, it should be the aim to secure a deep layer of 
thoroughly pulverized, aerated and fertilized soil. In 
the preparation of the seed bed the character and con- 
dition of the subsoil is equally as important as of the 
surface soil. 

337. Cultivation to Destroy Weeds. — One of the 

chief objects of cultivation is to destroy weeds. Cul- 
tivation for this purpose should be given early in the 



252 SOILS AND FERTlIvIZKRS 

year before the weeds become firmly established. 
Weeds are most easily destroyed at the time of germ- 
ination and before the leaves appear above ground. 
The plow should be relied upon largely for the de- 
struction of deep rooted perennial weeds, while the 
cultivator is effectual for the destruction of annuals. 
When weeds are plowed under or destroyed by culti- 
vation they add vegetable matter and humus to the 
soil and thus are made to improve the condition of 
the soil instead of reducing the yield of crops by 
appropriating fertility as they do if allowed to grow 
and mature. Cultivation which secures aeration of 
the soil and conservation of the soil moisture is also 
effectual for the destruction of weeds. 

338. Influence of Cultivation Upon Bacterial 
Action. — The cultivation of the soil has a marked 
influence upon bacterial action. Some of the soil 
organisms as the nitrifying organisms, (See Section 
139) require oxygen for their existence, hence culti- 
vation which increases the supply of oxygen in the 
soil increases the activity of such organisms. In acid 
peaty soils, aeration induces bacterial action which re- 
sults in more rapid decay and a lowering of the per 
cent, of total organic matter including the deleterious 
organic acids. The neutralizing of the organic acids 
of soils by applications of lime and wood ashes hastens 
bacterial action. During the process of nitrifica- 
tion, the bacterial action is not alone confined to the 
nitrogenous compounds of the soil, the nitrifying 
organisms require phosphates as food which are left 



PREPARATION OF SOILS FOR CROPS 253 

after nitrification in a more available condition as 
plant food9^ The mineral as well as the organic 
matter of the soil is subject to the action of micro- 
organisms, and the cultivation which the soil receives 
can be made either to accelerate or to retard this 
action. Many of the chemical changes which take 
place in the soil resulting in the liberation of plant 
food are induced by micro-organisms, hence the rela- 
tion between cultivation of the soil and bacterial 
action. Each type of soil has its own characteristic 
microscopic flora. 

339. Inoculation of Soils. — In old soils where 
the process of nitrification is feeble, it has been pro- 
posed to inoculate the soils with more active forms of 
bacteria so as to make the inert humus nitrogen more 
available as plant food. In order to secure the best 
results from inoculation, suitable food must be sup- 
plied for the organisms and any adverse condition, as 
excess of acids or alkalies, must be corrected. Most 
soils contain the requisite soil organisms but frequently 
they are unable to do their work because of unfavor- 
able soil conditions, as the presence of injurious matter 
or the lack of cultivation or food. For the production 
of legumes, inoculation of the soil is often beneficial. 
The commercial production and distribution of the 
organisms, forming the nodules on the roots of clover 
and other leguminous crops and which cause fixation 
of atmospheric nitrogen, was first proposed and inau- 
gurated by Nobbe94"; later a modified form of soil in- 
oculation was proposed by Moore^^, The method 



254 SOII.S AND FERTILIZERS 

of inoculation consists in first multiplying the organ- 
isms in water containing nutritive substances, and 
then sprinkling the seeds with this solution diluted. 
Inoculation with soil from a field where clover or 
lupines have previously been grown has also been suc- 
cessful, particularly in reclaiming sandy waste lands 
where mineral fertilizers containing potash and phos- 
phates are used to furnish these elements of plant food, 
while the more expensive nitrogen is acquired indi- 
rectly from the air through the clover. Soils in a 
high state of productiveness are not usually in need 
of inoculation as they already contain all of the essen- 
tial soil organisms. 

340. Cultivation for Special Crops. — While the 
general principles of cultivation apply to all crops, the 
extent to which loosening or compacting of a soil 
should be carried, must be determined by the charac- 
ter of the soil and the crop that is to be produced. 
The methods of cultivation must be varied to meet 
the requirements of different soils and different crops. 
The physical requirements of the soil for general farm 
crops are discussed in Chapters I. and XI. For the 
production of a special crop, the cultivation must be 
adapted to the specific requirements of that crop. A 
knowledge of the requirements can best be obtained 
by a study of the subject as based upon experimental 
evidence. The cultivation of an untried crop should 
not be attempted on a large scale without a knowledge 
of the food requirements and the most suitable soil 
conditions. The production of sugar beets for 



PREPARATION OF SOII.S FOR CROPS 255 

the manufacture of sugar, flax for fine fiber, or 
tobacco under shade, requires a high degree of 
both knowledge and skill. For the production of 
special crops the preparation of the seed bed and the 
subsequent cultivation of the crop are matters of prime 
importance, and should receive careful consideration 
on the part of the cultivator. Many times agricultural 
industries undertaken in new countries have failed 
because the cultivation of the special crop used in the 
industry has not been successfully accomplished on 
account of lack of knowledge of the cultural methods 
necessary for successful crop production. 

341. Cultivation to Prevent Washing and Gully- 
ing of Land. — In regions of heavy rain fall, rolling 
lands of clay texture often become gullied by the 
water flowing in large amounts over the surface. 
Under such conditions the preparation of a seed bed, 
and cultivation of the soil so as to prevent washing 
are often difficult problems. To prevent gullying, the 
water currents should be divided as much as possible 
by plowing narrower 'lands' and by increasing the num- 
ber of shallow dead furrows. The larger drains should 
be constructed with the view of preventing the forma- 
tion of deep gullies, this can in part be accomplished 
by encouraging the growth of special grasses with 
fibrous roots which serve as soil binders. Soils which 
gully are improved by the addition of farm manures 
and other humus forming materials which bind the 
soil particles ; also by seeding and cultivating at right 
angles to the slope of the land so as to break the force 



256 SOILS AND FERTILIZERS 

of the waterr The water should be encouraged to per- 
colate through the soil rather than to flow over the 
surface. (See Section 25). 

342. Bacterial Diseases of Soils. — Many of the 
bacterial diseases to which crops are subject are caused 
primarily by a diseased condition of the soil. These 
diseases can often be held in check by the right kind 
of cultivation, by securing good drainage and by proper 
soil ventilation supplemented with the application of 
alkaline matter as wood ashes and land plaster. Both 
bacterial and fungus diseases of soils are capable of 
being controlled by cultivation particularly when the 
cultivation improves the general sanitary condition of 
the soil. With the improvement of the sanitary con- 
dition, there is less liability of bacterial diseases becom- 
ing established and causing destruction of the crop. 
The use of soil disinfectants is possible only when a 
small area is involved ; they are not applicable to 
large tracts as they destroy the beneficial as well as 
the injurious soil organisms. A good sanitary condi- 
tion of the soil is as essential for the production of 
crops as are suitable hygienic surroundings for the 
rearing of live stock. Sunlight and air are important 
factors in bringing about an improved sanitary condi- 
tion of diseased soils. By the rotation of crops many 
bacterial diseases as flax wilt and clover sickness are 
held in check. Some bacterial diseases are dissemin- 
ated by the use of infected seed. By sprinkling the 
seed grain with a disinfectant as a dilute solution of 
formalin (i pound of formalin in 50 gallons of water) 



PREPARATION OF SOILS FOR CROPS 257 

bacterial diseases, as grain smuts are held in check. 
Low forms of plants, as fungi, also develop in soils 
when conditions are favorable, and they take an im- 
portant part in changing the character of the soil ; 
their action may be either beneficial or injurious de- 
pending upon the condition of the soil. Some of the 
organisms which are propagated in the soil cause bac- 
terial diseases of dairy and other farm products. There 
is a very close relationship between soil sanitation, 
crop diseases, and the quality of agricultural products. 

343. Influence of Crowding Plants in the Seed 

Bed. — The number of plants which a seed bed should 
produce is dependent mainly upon the supply of water 
and plant food. By means of thick or thin seeding 
the general character of crops may be influenced 
within definite limits. Either an excessive or a scant 
amount of seed gives poor results. If over crowded 
plants fail to develop normally it is either for want of 
plant food or water or because of lack of room for de- 
velopment. Experiments have shown that excessive 
amounts of seed wheat, as more than loo pounds per 
acre of spring wheat, do not give good results. Each 
crop has its limits beyond which it is not desirable to 
crowd the plants in the seed bed. When there is ex- 
cessive crowding, unhygienic conditions prevail and 
the lack of air, sunlight and good ventilation encourage 
bacterial diseases, while on the other hand too few 
plants in the seed bed favor the growth of weeds and 
an abnormal development of the crop. In the seeding 
of grains and other farm crops, the amount of seed to 

(17) 



258 SOII.S AND FKRTII.IZERS 

be used per acre should be determined by the quality 
of the seed and the local conditions, as climate and 
soil, together with any special objects desired as in- 
fluencing the composition and character of the crop. 

344. Selection of Crops. — The selection of the 
most suitable crops to be grown is largely a local 
problem and must be determined by climatic and soil 
conditions. The preferences of farm crops for certain 
types of soil are discussed in Sections 11 to 17, and it 
is not advisable to attempt to grow crops upon soils 
to which they are not naturally adapted or under un- 
favorable climatic conditions. Practical experience 
is the best guide to follow in regard to the selection 
of crops or the most suitable line of farming to follow, 
and it will be found that this experience is usually in 
harmony with the laws governing the conservation 
of the fertility of the soil. Temporary methods 
of farming, as exclusive grain raising, can be followed 
for a short time on new soils but it is desirable that 
each type of soil should be subjected to a judicious 
system of cultivation, fertilizing and cropping rather 
than to the production of one or only a few market 
crops at random. The selection of the farm crops 
and their utilization for market or feeding purposes 
should be determined mainly by the system of farming 
that is best adapted to the soil of the farm, and the 
farm should be managed largely with the view of 
maintaining the fertility of the soil. 

345. The Inherent and Cumulative Fertility of 
Soils95. — There is present in nearly every soil a vari- 



PRKPARATION OF SOILS FOR CROPS 259 

able amount of inherent fertility produced by disin- 
tegration and other changes to which soils are subject. 
In some long-cultivated soils the amount of fertility 
produced annually by weathering and natural agencies 
is sufficient to yield from 10 to 15 bushels of wheat. 
This does not represent the maximum crop producing 
power of the soil but simply the inherent or natural 
fertility. When the natural fertility is reinforced 
with farm manures and other fertilizers, cumulative 
fertility has been added and maximum yields of crops 
are secured. In many soils there are large amounts 
of cumulative fertility or residues from former appli- 
cations of manures. The condition of a soil as to crop 
producing power is dependent both upon the inherent 
and the cumulative fertility, as well as upon the 
mechanical condition of the soil. In the production 
of crops, it should be the aim to utilize all of the in- 
herent fertility to the best advantage, and to add to 
the cumulative fertility so that the stock of total fer- 
tility may be increased. Soils of the highest fertility 
are those which are composed of a large amount of 
silt or particles of equivalent value, are well drained, but 
sufficiently retentive of moisture for crop production, 
and are of good capillarity. Such soils have usually 
been deposited by water ; they are uniform in texture, 
of great depth and contain large amounts of organic 
matter rich in nitrogen and mineral matter contain- 
ing all of the essential elements of plant food. When 
such soils are cultivated, the organic matter readily 
undergoes decay with liberation of plant food. 

346. Balanced Soil Conditions. — A high state of 



26o SOILS AND FERTILIZERS 

fertility necessitates a balanced condition of the physi- 
cal and chemical properties of a soil. Some soils are 
of good texture and have all of the necessary physical 
requisites for crop production but fail to produce good 
crops because of a scant supply of the essential ele- 
ments of plant food. Other soils contain the neces- 
sary plant food but are unproductive because of poor 
physical conditions. Soils may be unproductive on 
account of either chemical or physical defects causing 
an unbalanced condition of the various factors of soil 
fertility. In the cultivation of a soil it should be the 
aim to discover any defect and then to apply the 
necessary corrective measures. Soil problems are ex- 
tremely varied in character and the cultivator of the 
soil should seek aid jointly from the sciences of chem- 
istry, physics, biology and geology, and also from prac" 
tical experience founded upon observations in the 
cultivation of soils and the production of crops. The 
utilization and maintenance of the fertility of the soil 
necessarily form the basis of any rational agricultural 
system. 



CHAPTER XIV 



LABORATORY PRACTICE 

The laboratory practice is an essential part of the work in Soils 
and Fertilizers as the experiments illustrate many of the funda- 
mental principles of the subject. The student should endeavor to 
cultivate his powers of observation so as to grasp the principles in- 
volved in the work rather than to do it in a mere mechanical or 
perfunctory way. Neatness is one of the essentials for success in 
laboratory practice ; an experiment performed in a slovenly way is 
of but little value. 

A careful and systematic record of the laboratory work should be 
kept by the student in a suitable note-book. In recording the re- 
sults of an experiment the student should give in a clear and con- 
cise form the following : 

( 1 ) Title of the experiment. 

(2) How the experiment is performed. 

(3) What was observed. 

(4) What the experiment proves. 

The note-book should be a complete record of the student's in- 
dividual work, and should be written up at the time the experi- 
ments are performed. 

The student is advised to review at the time the experiments are 
performed those topics presented in the text which have a bearing 
upon the experiments, so that a clearer conception can be gained 
of the relationship between the laboratory work and that of the 
class room. 

Students who have had but little laboratory practice are advised 
to study ttje chapters on I/aboratory Manipulation, and Water and 
Dry Matter, given in "The Chemistry of Plant and Animal Life." 

Some of the pieces of apparatus are loaned to the student when 
needed to perform the experiment ; for this apparatus a receipt is 
taken, and the student is credited with the apparatus when it is 
returned. The following are supplied to each student : 



262 



SOILS AND FERTILIZERS 



I Crucible Tongs. 

I Pkg. Filter Paper. 

I Test Tube Clamp. 

I Evaporator. 

I Stirring Rod. 

3 Beakers. 

6 Test Tubes. 

I Test Tube Stand. 

I Funnel. 

I Mortar and Pestle. 

The student should 
in the laboratory. 

Determination 
Weigh in grams to 



2 Bottles. 
I Large Cylinder. 
I Sand Bath. 
I Hessian Crucible. 
I Wooden Stand. 
I Tripod. 

I Ring Stand and 3 Rings. 
I Single Clamp. 

I Burner and 2Ft.RubberTubing 
I Brush, 
plan to make judicious use of his time while 

Experiment No. i. 
of the Hydroscopic Moisture of Soils, 
the second decimal place an aluminum dish 




Fig. 37. Apparatus for Determining Moisture Content of Soils. 
or tray. Place about ten grams of air dry soil in the dish and 
weigh again. Then place the dish containing the soil in the water 



EXPERIMENTS 263 

oven and leave it four hours for the soil to dry. Cool and weigh 
at once so there may be as little absorption of water from the air 
as possible. From the loss of weight, calculate the per cent, of 
hydroscopic moisture in the soil. (Soils from the students' home 
farms are to be used in experiments Nos. i, 2, 4, 6, 9, 12, 14, 16, 17, 
and 19, each student working with his own soil). 

Experiment No. 2. 
Determination of the Capacity of Loose Soils to Absorb Water. 

To 100 grams of air dry soil in a beaker, add 100 cc. of water. 
Mix the soil and water, then pour the mixture on a filter paper 
fitted into a funnel and previously saturated, but not dripping. 
For transferring the soil, 50 cc. more water may be used. Measure 
the drain water in a graduate. To prevent evaporation, keep the 
moist soil in the funnel covered with a glass plate. Deduct the 
leachings from the total water used. Calculate the per cent, of 
water retained by the air dry soil. 

Repeat the experiment, using sand, and note the difference in 
absorptive power. 

Repeat, using 95 per cent, of sand and 5 per cent., of dry and 
finely pulverized manure. 

Experiment No. 3. 
Determination of the Capillary Water of Soils. 
For this experiment, a sample of soil directly from the 
field is to be used. The sample is to be taken at a depth 
of from 3 to 9 inches or at any depth desired. One hundred 
grams of soil are weighed into a tarred drying pan, exposed 
in a thin layer to the room temperature for twenty-four hours and 
then reweighed. After an interval of from two to four hours the 
soil is weighed again, and if the weight is fairly constant the per 
cent, of water lost by air drying, representing the capillary water 
of the soil at the time of sampling, is calculated. If desired this 
experiment can be repeated, using different types of soil, as sand, 
clay and loam. 

Experiment No. 4. 
Capillary Action of Water Upon Soils. 
Firmly tie a piece of linen cloth over the end of a long glass tube 
4 inches in diameter, then fasten a piece of wire gauze over the 



264 



SOILS AND FERTILIZERS 



cloth. Fill the tube with sandy soil (No. i). Compact the soil 
after the addition of each measured quantity of soil by allowing the 
weight from the compaction machine to drop twice from the 12 
inch mark. 



- i 

' 1 


, m 

■J 


* 1 " 







Fig. 38. Capillary Action of Water 011 Soils. 
In a similar way, fill a second and a third tube respectively with 
clay and loam ; then immerse the lower ends of the tubes in a 
cylinder of water and support the tubes, as shown in the illustra- 
tion. Measure each day for one week the height to which the 
water rises in the soils. If desired, three additional tubes filled 
loosely with the soils can be used, and the influence of compaction 
upon the capillary rise of water in the soils noted. 

Experiment No. 5. 
Influence of Manure and Shallow Surface Cultivation Upon the 
Moisture Content and Temperature of Soils. 
Weigh and fill four boxes, each a foot square and a foot deep, as 



EXPERIMENTS 



265 



follows : One with air dry sand, one with clay, one with loam, and 
one with sand containing 5 per cent, of fine dry manure. Deter- 
mine the hydroscopic moisture of each sample. Weigh the boxes 
after adding the soils which should be moderately compacted. To 
each add the same amount of water slowly from a sprinkling pot, 
carefully measuring the water used. The soil should be well 
moistened, but not supersaturated. Each box is to receive shal- 
low surface cultivation, using for the purpose a gardener's small 
tool. Leave the boxes exposed to the sun or in a moderately warm 
room. At the end of two or three days take a sample of soil from 
the center of each box at a depth of four inches and determine the 
moisture content as directed in Experiment No. i. Note the diflfer- 
ences in moisture content. Weigh the boxes. Take the tempera- 
ture of the soil in each box. 

Experiment No. 6. 
Weight of Soils. 
Determine the cubic contents of a box about 4 inches square. 
Weigh the box. Determine its weight when filled, not compacted, 
with air dry sand, with clay, with loam and with peaty soil. Com- 
pute the weight per cubic foot of each soil. 




Fig. 39. Determining the Weight of Soils. 

Experiment No. 7. 

Influence of Color Upon the Temperature of Soils. 

Expose to thejsun's rays, dry clay, dry sand, and moist and dry 

peat. After two hours exposure take the temperature of each. 

The bulb of the thermometer should just be covered with the soil. 

All of the observations should be made under uniform conditions. 



266 SOILS AND FERTILIZERS 

Experiment No. 8. 
Movement of Air Through Soils. 
Fill a tube 12 inches high and 3 inches in diameter with sifted 
loam soil without compacting. Attach the soil tube to the aspira- 
tor by means of a rubber tube. Note the time required to draw 5 
liters of air through the soil. In like manner fill tubes with sand, 




Fig. 40. Apparatus to Determine Rate of Air Movement Through Soils. 
(Adapted from Bui. 107, U. S. Dept. Agr., Office of Expt. Stations). 

gravel, peat, and clay, and determine the time required for 5 liters 
of air to be aspirated through each. In filling the tubes, care 
should be taken that all are treated alike. Repeat the experiment 
using soil from your own farm loosel}' filling one tube, and mod- 
erately compacting another tube with the compacting machine. 
Note the difference in the time required for the air to pass through 
the loose and the compact soil. 

Experiment No. 9. 

Separation of Sand, Silt and Clay. 

For this experiment, the student should use some of the soil 
from his home farm. Ten grams of soil which have been passsd 
through a sieve with holes .5 mm. in diameter are placed in a mor- 



EXPERIMENTS 267 

tar, and about 20 cc. of water added. The soil is pestled with a 
rubber tipped pestle with the object of separating adhering parti- 
cles without pulverizing the individual soil grains. After two or 
three minutes rubbing, more water is added and the soil and water 
are allowed to sediment for about one minute ; the turbid liquid is 
then decanted into a beaker. This process of soft pestling and 
decantation is repeated two or three times until the remaining soil 
grains appear free from adhering smaller particles. With some 
soils this is a tedious process. The contents of the mortar are then 
transferred to the beaker and enough water is added to nearly fill 
the beaker. The contents of the beaker are thoroughly stirred, 
and after three to five minutes sedimentation, the turbid liquid is 
decanted into a second beaker leaving the sediment in the first 
beaker. More water is added to the first beaker and the process 
of stirring, sedimentation and decantation are repeated until the 
sediment consists mainly of clean and fine sand. The turbid liquid 
in the second beaker is decanted into a large cylinder ; the sedi- 
ment in the second being washed with more water and the wash- 
ing added to the cylinder. It is to be noted that the sediment in 
the second beaker is composed of finer particles than the sediment 
in the first beaker. The sediment in the first beaker consists 
mainly of medium and fine sand, and in the second beaker, of fine 
sand and coarse silt. Some sand particles are carried along in the 
washings into the large cylinder. It is difficult to make even an 
approximate separation of a soil into sand, silt and clay particles. 
In the mechanical analysis of soil, the chemist uses the microscope 
to determine when the separations are reasonably complete. The 
sediment in the cylinder consists mainly of silt. The fine parti- 
cles which remain suspended in the water of the cylinder and 
cause the roiled appearance are mainly the clay particles. In this 
experiment note approximately what grades of soil particles pre- 
dominate in your soil. Save the liquid in the cylinder for the next 
experiment.. 

Experiment No. 10. 

Sedimentation of Clay. 

In each of three separate cylinders or beakers place 200 cc. of the 

turbid liquid saved from Experiment No. 9. To beaker No. i, add 

.5 gm. calcium hydroxid and stir. To beaker No. 2, add i gm. 

of calcium hydroxid and stir. The third beaker is used for pur- 



268 SOILS AND FERTILIZERS 

poses of comparison and no calcium hydroxide is added. After 24 
hours examine the three beakers and note the influence of the cal- 
cium hydroxid in precipitating the clay and clarifying the liquid. 

Experiment No. 11. 
Properties of Rocks from which many Soils are Derived. 

Study the laboratory samples of rocks and fill out the following 
table : 

Comparative General Soluble 
Rocks. Hardness. Color. Form. in HCl 
Feldspar 

Quartz 

Granite 

Hornblende 

lyimestone 

Experiment No. 12. 
Form and Size of Soil Particles. 

(Note. Special directions for manipulating the microscope, 
placing the material on the microscopical slide, and focusing will 
be given by the instructor). 

Place on a microscopical object slide a small amount of soil, dis- 
tribute it in a thin layer, as directed by the instructor, and examine 
with a low power microscope. Observe the form and size of the 
soil particles, distinguish the various grades of sand, silt and 
clay, and make drawings of some of the particles. 

Experiment No. 13. 
Pulverized Rock Particles. 
Examine with a low power microscope samples of pulverized 
mica, feldspar, granite, and limestone. Note any similarity to the 
soil particles examined in Experiment No. 12. 

Experiment No. 14. 
Reaction of Soils. 
For this experiment use peaty, mildly alkaline and clay soils. 
Bring in contact with each soil, moistened with distilled water, 
pieces of sensitive red and blue litmus paper. Note any changes 
in color of the litmus paper and state what the results show. In 
a similar way test the soil from your own farm. 



EXPERIMENTS 269 

Experiment No. 15. 
Absorption of Gases by Soils. 
Weigh 50 grams of soil into a wide mouthed bottle, add 50 cc. of 
water and i cc. of strong ammonia. Note the odor. Cork the 
bottle, shake, and after 24 hours again note the odor. To what is 
the absorption of the ammonia due? Is this a physical or a chem- 
ical change. Define fixation. 

Experiment No. 16. 
Acid Insoluble Matter of Soils. 
Weigh 10 grams of soil into a beaker, add 100 cc. hydrochloric 
acid (50 cc. strong acid and 50 cc. HgO); cover the beaker with a 
watch glass ; heat on the sand bath in the hood for two hours, re- 
placing the acid solution, if necessary, in case excessive evapora- 
tion takes place. Filter, transfer and wash the residue, using 50 
cc. distilled water. Note the appearance and quantity of insoluble 
residue. Of what does it consist ? What is its value as plant food ? 
How does it resemble the original soil and in what ways does it 
differ? Save the filtrate for the next experiment. 

Experiment No. 17. 
Acid Soluble Matter of Soils. 
Divide the filtrate from the preceding experiment into three 
equal portions, (i) To one portion add ammonia until alkaline. 
The precipitate formed consists of iron and aluminum hydroxid and 
phosphoric acid. Note the color and gelatinous appearance of this 
precipitate. When dried it occupies only a small volume. Filter 
and remove this precipitate. This filtrate contains lime, magnesia, 
potash and soda. To the filtrate add 20 cc. of ammonium oxalate, 
warm on the sand bath and note any precipitate of calcium oxalate 
that is formed. (2) Evaporate the second portion nearly to dry- 
ness. Add 20 cc. distilled HgO and 3 cc. HNO3 5 warm to dissolve 
any residue. Add 5 to 7 cc. of ammonium molybdate, heat gently 
and shake. The precipitate is ammonium phosphomolybdate, 
which contains the element P in chemical combination. (3) 
Evaporate third portion in the evaporating dish on the sand bath. 
What does the residue consist of and what elements does it con- 
tain ? 



270 SOILS AND FERTILIZERS 

Experiment No. 18. 
Extraction of Humus from Soils. ^ 

Ten grams of soil are placed in a bottle (preferably a glass stop- 
pered one) and 200 cc. HgO and 5 cc. HCl added. Shake and 
allow 10 to 24 hours for the acid to dissolve the lime so that the 
humus can be dissolved by the alkali. Filter the acid and wash 
the soil on the filter with distilled water until the washings are no 
longer acid to litmus paper. Transfer the soil to the bottle again, 
add 100 cc. H2O and 5 cc. KOH solution. Shake, and after two to 
four hours filter off some of the solution, which is dark-colored 
and contains dissolved humus compounds. 

To 10 cc. of the filtered humus solution, add HCl until neutral. 
The precipitate that is formed is mainly humic acid and soil 
humates. Evaporate a second portion of 10 to 20 cc. to dryness ; 
the black residue obtained is humus material extracted from the 
soil. 

Experiment No. 19. 
Nitrogen in Soils. 

Mix 5 grams of soil and an equal bulk of soda lime in a mortar ; 
transfer to a strong test tube. Connect the test tube with a deliv- 
ery tube which leads into another test tube containing distilled 
water. Heat cautiously the test tube containing the soil and soda 
lime with the Bunsen burner, for from 5 to 10 minutes. Test the 
liquid with litmus paper and note the reaction. Soda lime aided 
by heat decomposes the organic matter of the soil and forms CO2' 
H2O and NH3. The nitrogen in the form of ammonia is distilled 
and absorbed by the water in the second test tube ; the reaction 
is due to the presence of the ammonia. 

Experiment No. 20. 

Testing for Nitrates. 
Dissolve about 50 milligrams of sodium or potassium nitrate in 
100 cc. H2O. To 15 cc. of this solution, add 2 cc. of a dilute and 
clear solution of FeSO^, and place the test tube in a cylinder. 
Through a long stemmed funnel add 2 or 3 cc. H2SO4. Observe 
the dark brown ring that is formed ; H.^SO^ liberates HNO3 as a 
free acid, which in turn changes the iron from the ferrous to the 
ferric state ; the dark brown color is due to the nitric acid forming 
intermediate iron compounds during .this operation. 



EXPERIMENTS 2 7 1 

Experiment No. 21. 
Volatilization of Ammonium Salts. 
In separate test tubes, place about .1 gm. each of ammonium car- 
bonate and ammonium sulphate. Apply heat gently to each and 
observe the result. Observe that the ammonium carbonate readily 
volatilizes and some is deposited on the walls of the test tube while 
the ammonium sulphate is much less volatile. In poorly venti- 
lated barns, deposits of ammonium carbonate are frequently found. 

Experiment No. 22. 

Testing for Phosphoric Acid. 

Dissolve .5 gm. bone ash in 15 cc. H2O and 3 to 5 cc. HNO3 and 

filter. To the warm filtrate, add 5 to 7 cc. ammonium molybdate 

and shake. The yellow precipitate formed is ammonium phospho- 

molybdate. See Experiment No. 17. 

Experiment No. 23. 

In a test tube, heat .5 gm. of bone ash with 20 cc. distilled 
H2O ; filter. To the warm filtrate, add 5 cc. ammonium molyb- 
date and shake. Note the result as compared with that when 
HNO3 was used with the distilled water. What does the result 
show ? 

Experiment No. 24. 
Preparation of Acid Phosphate. 

Place 100 gms. bone ash in a large lead dish. Add slowly and 
with constant stirring 100 gms. commercial sulphuric acid, using 
an iron spatula for the purpose. Transfer the mixture to a wooden 
box and allow it to act for about three days. Then pulverize and 
examine. The mixing of the acid and phosphate should be done 
in a place where there is a good draft. Test }i gram for water 
soluble phosphates as directed in Experiment No. 23. 

Experiment No. 25 
Solubility of Organic Nitrogenous Compounds in Pepsin Solution. 
Prepare a pepsin solution by dissolving 5 gms. of commercial 
pepsin in a litre of water, adding i cc. of strong HCl. Place in 
separate beakers .5 gm. each of dried blood, tankage and bone ash. 
Add 200 cc. of pepsin solution to each and place the beakers in a 
water bath kept at a temperature of about 40 deg. C. Stir occasion- 



272 SOILS AND FERTII.TZERS 

ally, and at the end of five hours observe the comparative amounts 
of insoluble matter remaining in the beakers, also the color and 
appearance of the solution in each beaker. See Section 158. 

Experiment No. 26. 
Preparation of Fertilizers. 
Mix in a box 200 gms. acid phosphate, (saved from Experiment 
24) 50 grams kainit, and 50 gms. sodium nitrate. Calculate the 
percentage composition of this fertilizer and its trade value. 

Experiment No. 27. 

Testing Ashes. 

Test samples of leached and unleached ashes in the way de- 
scribed in Section 240. 

Experiment No. 28. 
Extracting Water Soluble Materials from a Commercial Fertilizer. 

Dry and weigh a 7 cm. filter paper. Fit it in a funnel, and place 
in it 2 gms. of commercial fertilizer. Pass through the filter, a 
little at a time, a half litre of pure water at about 40 deg. C. (dis- 
tilled water preferred). Transfer the filter paper and contents to 
a watch glass, dry in a water oven, weigh and calculate the per 
cent, of material extracted by the water. If the fertilizer is made 
of such materials as acid phosphate, kainit, muriate or sulphate of 
potash, nitrate of soda and sulphate of ammonia, from 60 to 90 per 
cent, will dissolve. Inspect the insoluble residue and note if it is 
composed of dried blood, bones or animal refuse materials. In a 
high grade complete commercial fertilizer, from 40 to 80 per cent, 
or more should dissolve in water. 

Experiment Ko. 29. 

Influences of Continuous Cultivation and Crop Rotation upon the 

Properties of Soils. 

For this experiment, a soil that has been under continuous culti- 
vation, and also one of a similar character from an adjoining field 
where the crops have been rotated and farm manures have been 
applied, should be used. Make the following determinations with 
each soil : 

Weight per cubic foot. 

Capacity to hold water. 



EXPERIMENTS 273 

Note the color of each, and the percentages of nitrogen and 
humus obtained by chemical analysis. 

Experiment No. 30. 
Summary of Results of Tests with Home Soil. 

Hydroscopic moisture as determined in Experiment No. i. 

Capacity of the loose soil to absorb water in Experiment No. 2. 

Height of rise of capillary water in tube in Experiment No. 4. 

Weight per cubic foot in Experiment No. 6. 

Prevailing kind of soil particles in Experiment No. 9. 

Reaction of soil in Experiment No. 14. 

Amount of acid soluble matter in Experiment No. 17. 

Amount of humus extractive material in Experiment No. 18. 

Amount of lime. 

Crops most suitable for production upon this soil as indicated by 
physical and chemical tests. 

How does this agree with your experience with the crops raised 
on the soil ? 

Probable deficiencies or weak points as indicated by tests or past 
experience. 

What is the most suitable line of farming to follow with this soil 
in order to conserve its fertility ? 

Scheme of Soil Classification. 

(Adapted from Bureau of Soils Report, U. S. Dept. Agr). 

Coarse sand contains more than 20 per cent, of coarse sand and 
more than 50 per cent, of fine gravel, coarse sand, and medium 
sand, less than 10 per cent, of very fine sand, less than 15 per cent, 
of silt, less than 10 per cent of clay, and less than 20 per cent, of 
silt and clay. 

Medium sand contains less than 10 per cent, of fine gravel, more 
than 50 per cent, of coarse, medium, and fine sand, less than 10 
per cent, of very fine sand, less than 15 per cent, of silt, less than 
10 per cent, of clay, and less than 20 per cent, of silt and clay. 

Fine sand contains less than 10 per cent, of fine gravel and 
coarse sand, more than 50 per cent, of fine and very fine sand, less 
than 15 per cent, of silt, less than 10 per cent, of clay, and less 
than 20 per cent, of silt and clay. 

Sandy loam contains more than 20 per cent, of fine gravel, coarse 
sand and medium sand, more than^20 per cent, and less than 35 

(18) 



274 SOILS AND FERTILIZERS 

per cent, of silt, less than 15 per cent, of clay, and less than 50 per 
cent, of silt and clay. 

Fine sandy loam contains more than 40 per cent, of fine and 
very fine sand and more than 20 per cent, and less than 50 per 
cent, of silt and clay, usually containing 10 to 35 per cent, of silt 
and from 5 to 15 per cent, of clay. 

Silt loam contains more than 55 per cent, of silt and less than 25 
per cent, of clay. 

Loam contains less than 55 per cent, of silt, and more than 50 
percent, of silt and clay, usually containing from 15 to 25 per cent, 
of clay. 

Clay loam contains from 25 to 55 per cent, of silt, 25 to 35 per 
cent, of clay, and more than 60 per cent, of silt and clay. 

Clay contains more than 35 per cent, of clay. 

Sandy clay contains more than 30 per cent, of coarse, medium, 
and fine sand, less than 25 per cent, of silt, more than 20 per 
cent, of clay, and less than 60 per cent, of silt and clay. 

Silt clay contains more than 55 per cent, of silt and from 25 to 
35 per cent, of clay. 



REVIEW QUESTIONS 



CHAPTER I. 

I. From what are soils derived? 2. What are the physical prop- 
erties of soils ? 3. Why do soils differ in weight ? Arrange clay, 
sand, loam, and peat in order of weight per cubic foot. 4. When 
wet,what would be the order? 5. What is the absolute and what the 
apparent specific gravity of soils? 6. Define the terms : Skeleton, fine 
earth, fine sand, silt and clay. 7. What are the physical properties 
of clay ? 8. What are the forms of the soil particles ? 9. How do 
different types of soil vary as to the number of soil particles per 
gram of soil? 10. How is a mechanical analysis of a soil made? 
II. Why do certain crops thrive best on definite types of soil ? 12. 
What factors must be taken into consideration in determining the 
type to which a soil belongs? 13. Explain the mechanical struc- 
ture of a good potato soil. 14. How does a wheat soil differ in 
mechanical structure from a truck soil? 15. A good corn soil is 
also a good type for what other crops? 16. How much water is 
required to produce an average grain crop, and how do the rainfall 
and the water removed in crops during the growing season com- 
pare? 17. In what forms may water be present in soils? 18. 
What is bottom water and when may it be utilized by crops? 19. 
What is capillary water? 20. Explain the capillary movement of 
water. 21. Explain how the capillary and non-capillary spaces in 
the soil may be influenced by cultivation. 22. What is hydro- 
scopic water and of what value is it to crops ? 23. What is perco- 
lation ? 24. To what extent may losses occur by percolation ? 25. 
What are the factors which influence evaporation ? 26. What is 
transpiration ? 27. In what three ways may water be lost from the 
soil ? 28. Why does shallow surface cultivation prevent evapora- 
tion ? 29. Why is it necessary to cultivate the soil after a rain ? 

30. Explain the movement of the soil water after a light shower. 

31. What influence has rolling the land upon the moisture content 
of the soil ? 32. What is subsoiling and how does it influence 
the moisture content of soils? 33. What influence does early 
spring plowit^g exert upon the soil moisture ? 34. What is the 
action of a mulch upon the soil? 35. Why should different soils 
be plowed to different depths? 36. What is meant by the per- 
meability of a soil? 37. How may cultivation influence permea- 
bility of a soil ? 38. How may commercial fertilizers influence the 
water content of soils ? 39. Explain the physical action of well- 
prepared farm manures upon the soil and their influence upon the 
•soil water. 40. What is the object of good drainage? 41. Why 
does deforesting a region unfavorably influence the agricultural 
value of a country? 42. What are the sources of heat in soils? 43. 



276 SOILS AND FERTILIZERS 

To what extent does the color of soils influence the temperature ? 
44. What is the specific heat of soils ? 45. To what extent does 
drainage influence soil temperature? 46. How do manured and 
unmanured land compare as to temperature ? 47. What relation 
does heat bear to crop growth ? 48. What materials impart color 
to soils ? 49. What is the effect of loss of organic matter upon the 
color of soils? 50. What materials impart taste to soils? Odor? 
51. W^hat effect does a weak current of electricity have upon crop 
growth? 52. Do all soils possess the same power to absorb gases? 
Why? 

CHAPTER II. 

53. What is agricultural geology? 54. What agencies . have 
taken part in soil formation ? 55. How does the action of heat and 
cold aid in soil formation ? 56. Explain the action of water in 
soil formation. 57. What is glacial action, and how has it been an 
important factor in soil formation ? 58. Explain the action of 
vegetation upon soils. 59. How has the action of micro-organisms 
aided in soil formation ? 60. Explain the terms : Sedentary, 
transported, alluvial, colluvial, volcanic, and windformed soils. 
61. What is feldspar and what kind of soil does it produce? 62. 
Give the general composition of the following rocks and minerals 
and state the quality of soil which each produces : Granite, mica, 
hornblende, zeolites, kaolin, apatite, and limestone. 



CHAPTER III. 

63. What elements are liable to be the most deficient in soils? 

64, Name the acid- and base-forming elements present in soils. 

65. What are the elements most essential for crop growth? 66. 
State some of the different ways in which the elements present in 
soils combine. 67. Why is it customary to speak of the oxides of 
the elements and to deal with them rather than with the elements ? 
68. Do the elements exist in the soil in the form of oxides ? 69. 
What are double silicates ? 70. In what forms does carbon occur in 
soils ? 71. Is the soil carbon the source of the plant carbon ? 72. 
What can you say regarding the occurrence and importance of the 
sulphur compounds ? 73. What influence would o.io per cent, 
chlorine have upon the soil ? 74. In what forms does phosphorus 
occur in soils? 75. What is the principal form in which the nitro- 
gen occurs in soils? 76. What can be said regarding the hydrogen 
and oxygen of the soil ? 77. State the principal forms and the 
value as plant food of the following elements: Aluminum, potas- 
sium, calcium, sodium, and iron. .78. For plant food purposes, 
what three divisions are made of the soil compounds ? 79. Why 
are the complex silicates of no value as plant food? 80. Give the 
relative amounts of plant food in the three classes. 81. How is a 
soil analysis made? 82. What can be said regarding the economic 



REVIEW QUESTIONS 277 

value of a soil analysis? 83. What are some of the important facts 
to observe in interpreting results of soil analysis? 84. Under what 
conditions are the results most valuable? S5. Do the terms volatile 
matter and organic matter mean the same ? 86. How may organic 
acids be employed in soil analysis ? 87. Why are dilute organic 
acids used ? 88. Is the plant food equally distributed in both sur- 
face and subsoil ? 89. Do different grades of soil particles, from 
the same soil, have the same composition? 90. What are "alkali 
soils " ? 91. Why is the alkali sometimes in the form of a crust? 
92. Are all soils with white coating strongly alkaline? 93,- Give 
the treatment for improving an alkali soil. 94. How may a small 
" alkali spot " be treated? 95. What are the sources of the organic 
compounds of soils ? 96. How may the organic compounds of the 
soil be classified? 97. Explain the term humus. 98. How is the 
humus of the soil obtained ? 99. What is humification ? What is 
a huniate ? How are humates produced in the soil? 100. Explain 
how different materials produce humates of different value. loi. 
Arrange in order of agricultural value the humates produced from 
the following materials : Oat straw, sawdust, meat scraps, sugar, 
clover. 102. Of what value are the humates as plant food ? 103. 
How much plant food is present in soils in humate forms ? 104. 
What agencies cause a decrease of the humus content of soils? 
105. To what extent does humus influence the physical properties 
of soils? 106. What is humic acid? 107. What soils are most 
liable to be in need of humus? When are soils not in need of 
humus? 108. In what ways does* the humus of long-cultivated 
soils differ from that of new soils? 109. How many different 
methods of farming influence the humus content of soils? 



CHAPTER IV. 

no. What may be said regarding the importance of nitrogen as 
plant food? in. What are the functions of nitrogen in plant nu- 
trition ? 112. How may the foliage indicate a lack or an excess of 
this element? 113. In what three ways did Boussingault conduct 
experiments relating to the assimilation of the free nitrogen of the 
air? 114, Wha't were his results? 115. What conclusions did. 
Ville reach? 116. Give the results of Lawes and Gilbert's experi- 
ments. 117. How did field results compare with laboratory exper- 
iments? 118. In what ways were the conditions of field experi- 
ments different from those conducted in the laboratory? 119. 
Give the results of Hellriegel's and Wilfarth's experiments. 120. 
What is noticeable regarding the composition of clover root 
nodules? 121. Of what agricultural value are the results of Hell- 
riegel? 122. What is the source of the soil's nitrogen ? 123. How 
may the organic nitrogen compounds of the soil vary as to com- 
plexity ? 124. To what extent may the nitrogen in soils vary? 
125. To what extent is nitrogen removed in crops? 126. To what 
extent are nitrates, nitrites, and ammonium compounds found in 



278 SOII.S AND FERTII.IZKRS 

soils? 127. To what extent is nitrogen returned to the soil in 
rain-water? 128, How may the ratio of nitrogen to carbon vary- 
in soils ? Of what agricultural value is this ratio? 129. Under 
what conditions do soils gain in nitrogen content ? 130. What 
methods of cultivation cause the most rapid decline in the nitro- 
gen content of soils? 131. What is nitrification? 132. What are 
the conditions necessarj^ for nitrification ? and what are the food 
requirements of the nitrifying organism ? 133. Why is oxygen 
necessary for nitrification ? 134. How does temperature, moisture, 
and sunlight influence this process? 135. What part does calcium 
carbonate and other basic compounds take in nitrification? 136. 
How is nitrous acid produced? 137. What is denitrification ? 138. 
What other organisms are present in soils besides those which pro- 
duce nitrates, nitrites, and ammonia? 139. What chemical 
products do these various organisms produce ? 140. Why are soils 
sometimes inoculated with organisms? 141. Why does summer 
fallowing of rich lands cause a loss of humus and nitrogen? 142. 
What influence have deep and shallow plowing, and spring and 
fall plowing upon the available soil nitrogen ? 143. Into what 
three classes are nitrogenous fertilizers divided ? 144. How is dried 
blood obtained? What is its composition, and how is it used? 
145. What is tankage? How is it used, and how does it differ in 
composition from dried blood? 146. What is flesh meal? 147. 
What is fish scrap fertilizer, and what is its comparative value? 
148. What seed residues are used as fertilizer ? What is their 
value ? 149. What method is employed to detect the presence of 
leather, hair, and wool waste in fertilizers ? Why are these ma- 
terials objectionable ? 150. How may peat and muck be used as 
fertilizers? 151. What is sodium nitrate? How is it used, and 
what is its value as a fertilizer ? 152. How does ammonium sul- 
phate, as a fertilizer, compare in value with nitrate of soda? 153. 
What is the difierence between the nitrogen content and the am- 
monia content of fertilizers? 



CHAPTERS V AND VI. 

154. What is fixation? Give an illustration. 155. To what is 
fixation due? 156. What part does humus take in fixation? 157. 
Why do soils differ in fixative power ? Why are nitrates not fixed ? 
158. Why is fixation a desirable property of soils? 159. Why is it 
necessary to study the subject of fixation in the use of manures? 
160. Why are farm manures variable in composition ? 161. What 
is the distinction between the terms stable manure and farm-yard 
manure? 162. About what per cent, of nitrogen, phosphoric acid, 
and potash is present in ordinary manure? 163. Coarse fodders 
cause an increase of what element in the manure ? 164. What 
four factors influence the composition and value of manure? 165. 
What influence do absorbents have upon the composition of 
manures ? 166. What advantages result from the use of peat and 



RKVIKW QUESTIONS 279 

muck as absorbents ? 167. Comoare the value of manure produced 
from clover with that from timothy hay. 168. How may the value 
of manure be determined from the nature of the food consumed ? 
169. To what extent is the fertility of the food returned in 
the manure? 170. Is much nitrogen added to the body during the 
process of fattening? 171. Explain the course of the nitrogen of 
the food during digestion and the forms in which it is voided in 
the manure. 172. Compare the solid and liquid excrements as to 
constancy of composition and amounts produced. 173. What is 
meant by the manurial value of food ? 174. Name five foods with 
high manurial values ; also five with low manurial values. 175. 
What is the usual commercial value of manures compared with 
commercial fertilizers ? 176. How does the manure from young 
and from old animals compare as to value? 177. How much 
manure does a well-fed cow produce per day? 178. What are the 
characteristics of cow manure ? How do horse manure and cow 
manure differ as to composition, character and fermentability ? 
179. What are the characteristics of sheep manure? 180. How 
does hen manure differ from any other manure ? i8r. Why should 
the solid and liquid excrements be mixed to produce balanced 
manure? 182. What volatile nitrogen compound may be given off 
from manure ? 183. What may be said regarding the use of human 
excrements as manure? 184. Is there any danger of an immediate 
scarcity of plant food to necessitate the use o f human excrements 
as manure? 185. To what extent may losses occur when manures 
are exposed in loose piles and allowed to leach for six months? 
186. What two classes of ferments are present in manure? 187. 
Explain the workings of the two classes of ferments found in 
manures. 188. How much heat may be produced in manure dur- 
ing fermentation ? 189. Is water injurious to manure? 190. How 
should manure be composted? What is gained ? 191. How does 
properly composted manure compare in composition with fresh 
manure ? 192. Explain the action of calcium sulphate in the pre- 
servation of manure. 193. How does manure, produced in open 
barnyards compare rn composition with that produced in covered 
sheds ? 194. When may manure be taken directly to the field and 
spread? 195. How may coarse manures be injurious to crops? 
196. What is gained by manuring pasture land ? 197. Is it econom- 
ical to make a number of small manure piles in a field ? Why? 
198. At what rate per acre may manure be used? 199. To what 
crops is it not advisable to add stable manure ? 200. How do a 
crop and a manure produced from that crop compare in manurial 
value? 2or. Why do manures have such a lasting effect upon 
soils? 202. Why does manure from different farms have such 
variable values and composition ? 203. In what seven ways may 
stable manures be beneficial ? 



CHAPTER VII. 

204. What may be said regarding the importance of phosphorus 



28o SOILS AND FERTILIZERS 

as plant food? What function does it take in plant economy? 
205. How much phosphoric acid is removed in ordinary farm 
crops ? 206. To what extent is phosphoric acid present in soils ? 
207. What are the sources of the soil's phosphoric acid? 208 What 
are the commercial sources of phosphate fertilizers ? 209. Give 
the four calcium phosphates and their relative fertilizer values. 
210. Deiiue reverted phosphoric acid. 211. Define available phos- 
phoric acid. 212. In what forms do phosphate deposits occur? 
213. State the general composition of phosphate rock. 214. Ex- 
plain the process by which acid phosphates are made. Give re- 
actions. 215. How is the commercial value of phosphoric acid de- 
termined? 216. What is basic phosphate slag and what is its value 
as a fertilizer? 217. What is guano? 218. How do raw^ bone 
and steamed bone compare as to field value ? As to composition ? 
219. What is dissolved bone? 220. How is bone-black obtained, 
and what is its value as a fertilizer? 221. How are phosphate fer- 
tilizers applied to soils ? In what amounts? 222. How may the 
phosphoric acid of the soil be kept in available condition ? 



CHAPTER VIII. 

223. What is the function in plant nutrition of potassium? 224. 
To what extent is potash removed in farm crops? 225. To what 
extent is potash present in soils? 226. What are the sources of 
the soil's potash? 227. What are the various sources of the potash 
used for fertilizers ? 228. What are the Stassfurt salts, and how 
are they supposed to have been formed ? 229. What is kainit ? 
230. How much potash is there in hard-wood ashes? 231. In 
what ways do ashes act on soils? 232. How do unleached ashes 
differ from leached ashes? 233. What is meant by the alkalimetry 
of an ash ? 234. Of what value, as fertilizer, are hard- and soft- 
coal ashes? 235. What is the fertilizer value of the ashes from 
tobacco stems? 236. Cottonseed hulls? 237. Peat-bog ashes? 
238. Saw-mill ashes? 239. Lime-kiln ashes? 240. How is the 
commercial value of potash determined? 241. How are potash 
fertilizers used? 242. Why is it sometimes necessary to use a lime 
fertilizer in connection with a potash fertilizer? 



CHAPTER IX. 

243. What can be said regarding the importance of lime as a 
plant food? 244. To what extent is lime removed in crops? 245. 
To what extent do soils contain lime ? 246. What are the lime fer- 
tilizers? 247. Explain the physical action of lime fertilizers. 248. 
Explain the action of lime on heavy clays. 249. On sandy soils. 
250. In what ways, chemically, do lime fertilizers act? 251. How 
may lime aid in liberating potash? 252. What is marl? 253. How 



REVIEW QUESTIONS 28 1 

are lime fertilizers applied ? 254. What is the result when land 
plaster is used in excess? 255. Explain the action of salt on soils. 
256. When would it be desirable to use salt as a fertilizer? 257. Is 
soot of any value as a fertilizer? Explain its action. 258. Are sea- 
weeds of any value as fertilizer? 



CHAPTER X. 

259. What is a commercial fertilizer? An amendment? 260. 
To what does the commercial fertilizer industry owe its origin ? 

261. Why are commercial fertilizers so variable in composition? 

262. Explain how a commercial fertilizer is made, 263. Why are 
the analysis and inspection of fertilizers necessary? 264. What 
are the usual forms of nitrogen in commercial fertilizers? 265. Of 
phosphoric acid and potash ? 266, How is the value of a commer- 
cial fertilizer determined ? 267. What is gained by home mixing 
of fertilizers? 268. What can be said about the importance of 
tillage when fertilizers are used ? 269. How are commercial fer- 
tilizers sometimes injudiciously used? 270. How may field tests 
be conducted to determine a deficiency in available nitrogen, phos- 
phoric acid, or potash? 271. To determine a deficiency of two 
elements? 272. How are the preliminary results verified ? 273. 
Why is it essential that field tests with fertilizers be made? 274. 
Under what conditions does it pay to use commercial fertilizers ? 
275. What is the result when commercial fertilizers are used in 
excessive amounts? 276. Under ordinary conditions, what special 
help do the following crops require : Wheat, barley, corn, potatoes, 
mangels, turnips, clover and timothy? 277. In what ways do 
commercial fertilizers and farm manures differ ? 



CHAPTER XI. 

278. Does the amount of fertility removed by crops indicate the 
nature of the fertilizer, required? In what ways are plant ash 
analyses valuable ? 27^. Explain the action of plants in render- 
ing their own food soluble. 280. Why do crops differ as to their 
power of procuring food? 281. Why is wheat less liable to need 
potash than nitrogen ? 282. What position should wheat occupy 
in a rotation ? 283. In what ways do wheat and barley differ in 
feeding habits ? 284. What can be said regarding the food require- 
ments of oats ? 285. Corn removes from the soil twice as much 
nitrogen as a wheat crop, yet a wheat crop usually thrives after a 
corn crop. Why ? 286. What help is corn most liable to need in 
the way of food? 287. What position should flax occupy in a 
rotation ? On what soils does flax thrive best ? 289. What is the 
essential point to observe in the manuring of potatoes ? 290. What 
kind of manuring do sugar-beets require ? 291. Why should the 



282 SOILS AND FERTILIZERS 

manuring of mangels be different from that of turnips? 292, What 
may be said regarding the food requirements of buckwheat and 
rape ? 293. What kind of manuring do hops and cotton require? 
294. What kind of manuring is most suitable for leguminous 
crops ? For garden crops, for orchards, or lawns ? 



CHAPTER XII. 

295. What is the object of rotating crops? 296. Should the 
whole farm undergo the same rotation system ? 297. What is 
meant by soil exhaustion ? 298. What are the nine important 
principals to be observed in a rotation ? 299. Explain why it is 
essential that deep and shallow rooted crops should alternate ? 
300, Why is it necessary that the humus be considered in a rota- 
tion ? 30 r. What is the object of growing crops of dissimilar feed- 
ing habits ? 302. How may crop residues be used to the best 
advantage? 303. In what ways may a decline of soil nitrogen be 
prevented by a good rotation of crops ? 304. In what ways do 
different crops and their cultivation influence the mechanical con- 
dition of the soil ? 305. How may the best use be made of the soil 
water ? 306, How may a rotation make an even distribution of 
farm labor? 307, How are manures used to the best advantage in 
a rotation ? 308. In what other ways are rotations advantageous ? 

309. What may be said regarding long and short-course rotations ? 

310. How is the conservation of fertility best secured ? 311. Why 
does the use made of crops influence fertility ? 312. What are the 
essential points to be observed in the two systems of farming com- 
pared in Section 323? 313. Is it essential that all elements re- 
moved in crops should be returned to the soil in exactly the 
amounts contained in the crops? Why ? 314. How does manure 
influence the inert matter of the soil ? 315. What general systems 
of farming best conserve fertility? 316. Under what conditions 
may farms be gaining in reserve fertility ? 317. Why in continued 
grain culture does the loss of nitrogen from a soil exceed the 
amount removed in the crop? 



CHAPTER XIII. 

318. Why do soils need further treatment for the preparation of 
the seed bed? 319. Why should different soils receive different 
methods of treatment in the preparation of the seed bed? 320, 
How would you determine the best treatment to give a soil for the 
preparation of the seed bed? 321. How do different methods of 
plowing influence the condition of the seed bed ? 322. Why does 
complete inversion of sod frequently form a poor seed bed ? 323. 
How should the plowing be done to form a good seed bed? 324. 
Why is it economy to pulverize the soil as much as possible when 
it is plowed? 325. What effect does the moisture content of the 



RBVIKW QUESTIONS 283 

soil at the time of plowing have upon the condition of the seed 
bed ? 326. What efifect does an excess of moisture have upon the 
plowing and working of clay soils? 327. In what condition 
should the seed bed be left as to fineness ? 328. What is gained 
by fining and moderately firming the seed bed ? 329. Why is. 
aeration of the soil necessary? 330. Why do different soils re- 
quire different amounts of aeration? 331, Under what conditions 
can the seed bed be prepared without plowing? 332. On what 
kinds of soil is such a practice not advisable? 333. When is it 
advisable to mix the sub soil with the surface soil ? 334. When 
is it not advisable to mix the surface soil and sub soil? 335. 
How can the plowing and the cultivation of the soil best be carried 
on to destroy weeds? 336. In what way does cultivation influ- 
ence bacterial action in the soil? 337. What classes of com- 
pounds in the soil are subject to bacterial action? 338. How does 
the action of bacteria affect the supply of available plant food ? 
339. What is meant by the inoculation of soils? 340. In what 
two ways can this be accomplished? 341. What soils are most 
improved by inoculation ? 342. What soils are least in need of 
inoculation ? 343. What other treatment must often be combined 
with inoculation? 344. Why do different crops require different 
cultivation ? 345. How can the best kind of cultivation for a crop 
be determined? 346. How can soils best be cultivated to prevent 
washing and gullying? 347. What treatment should such soils 
receive to be permanently improved? 348. What relationship 
exists between bacterial diseases of soils and crops? 349. What 
treatment should soils receive to prevent bacterial diseases? 350. 
How can the spreading of bacterial diseases through infected seed 
be prevented? 351. Why must the sanitary condition of a 
soil for crop production be considered? 352. What effects da 
some forms of fungi have upon soils? 353. In what way does 
thick or thin seeding'affect plant growth? 354. What effect does 
abnormal crowding of plants have upon growth? 355. How 
would you determine the most advantageous quantity of seed for 
crop production ? 356. How would you determine the most suit- 
able crop for production upon any soil? 357. What should be 
the aim in the selection of crops for soils? 358. Why should the 
crop selected vary with different types of soil? 359. What is the 
inherent fertility of soils ? 360. What is the cumulative fertility 
of soils? 361. How can the total fertility of soils be best in- 
creased? 362. Describe soils of the highest fertility. 363, Why 
must the amount of plant food as well as the physical condition of 
the soil be considered in the improvement of soils? 364, What 
relation does the fertility of the soil bear to any agricultural 
system ? 



REFERENCES 

1. Venable : History of Chemistry. 

2. Gilbert : Inaugural Lecture, University of Oxford. 

3. Liebig : Chemistry in Its Applications to Agriculture and 
Physiology. 

4. Gilbert: The Scientific Principles of Agriculture (Lecture). 

5. Minnesota Agricultural Experiment Station, Bulletin No. 30. 

6. Stockbridge : Rocks and Soils. 

7. Association of Official Agricultural Chemists, Report 1898. 

8. Maryland Agricultural Experiment Station, Bulletin No. 21. 

9. Minnesota Agricultural Experiment Station, Bulletin No. 41. 

10. Osborne : Journal of Analytical Chemistry, Vol. II, Part 3. 

11. Wiley : Agricultural Analysis, Vol. I. 

12. Hellriegel : Calculated from Beitrage zu den Naturwissen- 
schaft Grandlagen des Ackerbaus. 

13. King : Wisconsin Agricultural Experiment Station, Report 
1889. 

14. Unpublished results of author. 

15. King : Soils. 

16. Roberts : Fertility of the Land. 

17. Minnesota Agricultural Experiment Station, Bulletin No. 41. 

18. Minnesota Agricultural Experiment Station, Bulletin No. 53. 

19. Whitney : Division of Soils, U. S. Department of Agriculture, 
Bulletin No. 6. 

20. Merrill : Rocks, Rock-weathering and Soils. 

21. Miintz : Comptes Rendus de 1' Academic des Sciences, CX 
(1890). 

22. Storer : Agriculture, Vol. I. 

23. Dyer: Journal of the Chemical Society, March, 1894. 

24. Goss : Association of Official Agricultural Chemists, Report 
1896. 

25. Peter : Association of Official Agricultural Chemists, Report 

1895. 

26. Loughridge : American Journal of Science, Vol. VII (1874). 

27. Hilgard : Year-book U. S. Department of Agriculture, 1895. 

28. Houston : Indiana Agricultural Experiment Station, Bulle- 
tin No. 46. 



REFERENCES 285 

29. Mulder : From Mayer : Ivchrbuch der Agrikulturchemie, 2. 

30. Journal of the American Chemical Society, Vol. XIX, No. 9. 

31. Year-book U. S. Department Agriculture, 1895. 

32. Loughridge : South Carolina Agricultural Experiment Sta- 
tion, Second Annual Report. 

33. Association of Official Agricultural Chemists, Report 1893. 

34. Washington Agricultural Experiment Station, Bulletin 
No. 13. 

35. Association of Official Agricultural Chemists, Report 1894. 

36. California Agricultural Experiment Station, Report 1890. 

37. Minnesota Agricultural Experiment Station, Bulletin No. 29. 

38. Minnesota Agricultural Experiment Station, Bulletin No. 47. 

39. Lawes and Gilbert : Experiments on Vegetation, Vol. I. 

40. Boussingault : Agronomic, Tome I. 

41. Atwater : American Chemical Journal, Vol. VI, No. 8 and 
Vol. VIII, No. 5. 

42. Hellriegel : Welche Stickstoff Quellen stehen der Pflanze zu 
Gebote ? 

43. Minnesota Agricultural Experiment Station, Bulletin No. 34. 

44. Warington : U. S. Department of Agriculture, Office of Ex- 
periment Stations, Bulletin No. 8. 

45. Hilgard : Association of Official Agricultural Chemists, Re- 
port 1895. 

46. Marchal : Journal of the Chemical Society (abstract), June, 
1894. 

47. Kiinnemann : Die Landwirthschaftlichen Versuchs-Sta- 
tionen, 50 (1898). 

48. Adametz : Abstract, Biedermann's Centralblatt fiir Agrikul- 
turchemie, 1887. 

49. Atwater: American Chemical Journal, Vol. IX (1887). 

50. Stutzer : Biedermann's Centralblatt fiir Agrikulturchemie, 
1883. 

51. Jenkins: Connecticut State Agricultural Experiment Sta- 
tion, Report 1893. 

52. Wagner : Biedermann's Centralblatt fiir Agrikulturchemie, 
1897. 

53. Journal of the Royal Agricultural Society, 1850. 

54. From Sachsse : Lehrbuch der Agrikulturchemie. 

55. lyawes and Gilbert : Experiments with Animals. 



286 SOILS AND FERTILIZERS 

56. Beal : U. S. Department of Agriculture, Farmers' Bulletin 
No. 21. 

57. Minnesota Agricultural Experiment Station, Bulletin No. 26. 

58. Mainly from Armsby : Pennsylvania Agricultural Experi- 
ment Station, Report 1890. Figures for grains calculated from 
original data. 

59. Heiden : Dungelehre. 

60. Liebig : Natural Laws of Husbandry. 

61. Cornell University Agricultural Experiment Station, Bulle- 
tins Nos. 13, 27 and 56. 

62. Kinnard : From Manures and Manuring by Aikman. 

63. Wyatt : Phosphates of America. 

64. Wiley : Agricultural Analysis, Vol. III. 

65. Goessmann : Massachusetts Agricultural Experiment Station, 
Report 1894. 

66. Connecticut (State) Agricultural Experiment Station, Bulle- 
tin No. 103. 

67. Goessmann: Massachusetts Agricultural Experiment Station, 
Report 1896. 

68. Wheeler : Rhode Island Agricultural Experiment Station, 
Reports 1892, 1893, etc. 

69. Boussingault : From Storer : Agriculture. 

70. Handbook of Experiment Station Work. 

71. New York (State) Agricultural Experiment Station, Bulle- 
tin No. 108. 

72. Voorhees : U. S. Department of Agriculture, Farmers' Bul- 
letin No. 44. 

73. Liebig : Die Chemie in ihrer Anvv^endung auf Agrikultur 
und Physiologic. 

74. Warington : Chemistry of the Farm. 

75. Lawes and Gilbert : Growth of Wheat. 

76. Lawes and Gilbert : Growth of Barley. 

77. Lugger : Minnesota Agricultural Experiment Station, Bulle- 
tin No. 13. 

78. Lawes and Gilbert : Growth of Potatoes. 

79. Minnesota Agricultural Experiment Station, Bulletin No. 56. 

80. Shaw : U. S. Department or Agriculture, Farmers' Bulletin 
No. II. 

81. White : U. S. Department of Agriculture, Farmers' Bulletin 
No. 48. 



REFERENCES 287 

'&2. Lawes and Gilbert : Permanent Meadows. 

83. Thompson : Graduating Essay, Minnesota School of Agri- 
culture. 

84. Nefedor : Abstract, Experiment Station Record, Vol. X, No. 4, 

85. Minnesota Agricultural Experiment Station, Bulletin No. 89. 

86. Journal Analytical and Applied Chemistry, Vol. VII, No. 6. 

87. Moore : U. S. Department of Agriculture, Bureau of Plant 
Industry, Bulletin No. 71. 

88. Meyer : Outlines of Theoretical Chemistry. 

89. Voorhees : Fertilizers. 

90. Cornell University Experiment Station, Bulletin No, 103. 

91. Fraps : Annual Report .1904, Association Official Agricultural 
Chemists. 

92. Illinois Experiment Station, Bulletin No. 93. 

93. Canadian Experiment Farms, Report 1903. 

94. D, Land. Vers. Stat., 1899, 52. 

95. A. D. Hall : The Soil. 



INDEIX 



Absorbents 133 

Absorption of heat by soils • • 39 

of gases by soils 269 

Absorptive power of soils- . • 43 

Acid soils 85 

Acid soluble matter, of 

soils.. 65, 269 

Acids in plant roots 218 

Aeration of soils 250 

Aerobic ferments 147 

Agricultural geology 45 

Agronomy 8 

Air movement through soils • 266 

Albite 52 

Alchemy i 

Alkaline soils 83 

Aluminum of soils 63 

Amendments, soils 196 

Amonium compounds 109 

salts — .129 

Anaerobic ferments 148 

Analysis of soil, how made- • 72 

value of 74, 78 

Apatite rock 54 

Apparatus, list of 262 

Application of fertilizer 212 

of manures 151, 154 

Arrangement of soil parti- 
cles 14 

Ashes 182 

action of, on soils 183 

testing of 272 

Assimilation of nitrogen 97 

of phosphates 165 

Atmospheric nitrogen 99 



Atwater 102, 125 

Availability of plant food. ■ . 77 

Available phosphates ... 168, 175 

nitrogen 108, 126 

Bacterial action and cultiva- 
tion 115, 252 

Barley, fertilizers for 213 

food requirements of. .220 

Blood, dried 121 

Bone, dissolved 174 

fertilizers 173 

Boneash 1 73 

Bone-black 174 

Boussingault's experiments. 

100, loi, 399 

Calcium as essential element. 187 
carbonate and nitrifi- 
cation 116 

compounds of soils. . • 64 

phosphate 55 

Capillary water, determina- 
tion of 263 

Capillarity 24 

and cultivation 29 

Carbon of soil 60 

sources for plant 

growth 60 

Chlorine of soil 61, 83 

Citric acid, use of in soil 

analysis 70 

Classification of soils, scheme 

for 273 



INDEX 



289 



Clay, formation of 54 

particles 12 

sedimentation of 267 

Clover as manure 127 

nitrogen returned by- 

102, 112, 245 

root nodules 104 

manuring of 226 

Coal ashes 184 

Color of plants, influenced 

by nitrogen 98 

of soils 41 

and soil temperature • • 265 

Combination of elements in 

soils 58 

Commei-cial fertilizers ..196-214 

abuse of 206 

and tillage 206 

and farm manures 214 

composition of 197 

extent of use 196 

field tests with 208 

for special crops 213* 

home mixing of 204 

inspection of 200 

judicious use of 207 

mechanical condition 

of 200 

misleading statements. 203 

nitrogen of 200 

phosphoric acid of 201 

plant food in 199 

potash of 202 

preparation of 197 

valuation of 203 

variable composition .197 

Composition of soils 80, 82 

Composting manures 149 

Corn, fertilizers for 213 

food requirements of. .221 
and manure 155 



Cotton, fertilizers for 224 

Cottonseed meal 1 25 

Cow manure 141 

Crop residue 232 

Cultivation after rains 32 

and bacterial action.. 252 

shallow surface 30 

and soil moisture 265 

Cumulative fertility 259 

Davy, work of 3 

Deficiency of nitrogen . . 209 

of phosphoric acid 210 

of potash 210 

of two elements 211 

Denitrification 117 

De Saussure, work of 3, 99 

Diseases of soils 256 

Dissolved bone 174 

Distribution of soils 50 

Drainage 28, 40 

Dried blood 121 

Early truck soils 17 

Electricity of soil 43 

Evaporation 27 

Excessive use of fertilizers. .212 

Experiments 261, 274 

Experimental plots 208 

Fallow fields 1 19 

Fall plowing 34 

Farm manures 131, 159 

and commercial fertil- 
izers 214 

Feldspar 52, 199 

Fermentation of manures. .147 
Fertility, conservation of... 241 

importance of 260 

removed in crops 216 



290 



INDEX 



Fertilizers, amount to use. . .212 
influence upon soil 

water 37 

on barley 213 

on wheat 213 

Field tests with fertilizers . . . 208 

Fine earth 11 

Fish fertilizer 125 

Fixation 1 60 

of ammonia 161 

due to zeolites 160 

nitrates not fixed 161 

and available plant 

food 162 

Flax, food requirements of. .222 

soils 19 

Flesh meal ....124 

Forest fires 92 

Formation of soils 45, 50 

Form of soil particles 14 

Fruit soils 18 

Fruit trees, fertilizers for. . .228 

Gains of humus 95 

of nitrogen iii 

Garden crops, fertilizers for. 226 
Geological study of soil, 

value of 56 

Glaciers, action of 47 

Grain soils 19 

Granite 54 

Grass lands, fertilizers for. . .225 

Grass soils 19 

Guano 172 

Gullying of soils 255 

Gypsum and manure 149 

Hay land, fertilizing 225 

Heat and crop growth 41 

produced by manures. 148 
of soil 39-40 



Heiden 145, 150 

Hellriegel 22, 28, 105 

Hen manure 143 

Hog manure 143 

Hops, fertilizers for 225 

Hornblende 52 

Horse manure 142 

Human excrements 145 

Humates 87 

as plant food 90 

Humification 87 

Humic acid 94 

Humic phosphates 88, 176 

Humus 87 

active and inactive . . • 95 

causes fixation 161 

composition of 90 

extraction of, from 

soils- 270 

loss of, from soils 92 

soils in need of 94 

Hydroscopic moisture 26 

determination of 262 

Importance of field trials 211 

Income and outgo of fertil- 
ity 242-245 

Infected seed and soil dis- 
eases 256 

Inherent fertility 259 

Injury of coarse manures. 38, 152 

Inoculation of soils 119, 253 

Insoluble matters of soils- 67-68 
Iron compounds of soil 65 

Kainit 180, 204 

Kaolin 54 

King 31, 33, 34 

Laboratory note book 261 

practice 262-274 



INDEX 



291 



Lawes and Gilbert. • -6, T02, 219 

Lawn fertilizers 228 

Leached ashes 183 

Leaching of manure 146 

Leather 126 

Leguminous crops, fertilizers 

for 226 

as manure 127 

nitrogen assimilations 

of 102-105 

Liebig 5, 6, 145, 216 

Liquid manure 136 

Lime, action on soils 189 

amount of, in soils . . '188 
amount removed in 

crops 188 

excessive use of 192 

fertilizers 188 

indirect action of 190 

physical action of 189 

use of 192 

and acid soil 189 

and clover 190 

Loam soils 22 

Loss of fertility in grain farm- 
ing • 243 

Loss of humus 292 

nitrogen iii, 119 

Losses from manures 146-7 

Magnesium compounds of 

soils 64 

salts as fertilizers 193 

Mangels, fertilizers for 214 

Manure from cow 141 

ben 143 

hog 143 

horse 142 

sheep 142 

Manures, farm 131 

composition of* 132 



Manures, composting of 149 

crop producing value. 139 
direct application of. -151 

fermentation of 147 

influence of, on soil 

temperature 264 

on moisture 264 

influenced by foods.. 134 

leaching of 146 

liquid 136 

mixing of 144 

and soil water 37, 93 

use of 151, 154 

use of in rotation 235 

value of 158 

Manurial value of foods 138 

Manuring of crops 154 

pasture land 152 

Marl 191 

Mechanical analysis of soils. 15 
condition of fertilizers. 200 
Methods of farming, influ- 
ence of, upon fertil- 
ity • 95 

Mica 53 

Micro-organisms and soil for- 
mation 45, 49, 

Mixing manures 144 

Movement of water after 

rains 32 

Mulching 35 

Nitrate of soda 128 

Nitric nitrogen 128 

Nitrification 113 

conditions n e c e s s ary 
for 113 

and plowing 120 

Nitrogen, assimilation ..99, 102 

of clover plant • • . 102, 105 

as plant food 97 



292 



INDEX 



Nitrogen, compounds of soil. 61 
compounds, solubility 

of 271 

deficiency of, in soil • • 209 
loss of, by fallowing.. 1 19 

losses of, from soil 1 1 1 

ratio of, to carbon no 

removed in crops 108 

in commercial fertil- 
izers 200 

amount of, in soils- -.107 

in organic forms 106 

as nitrates 109 

availability of • 107 

forms of 106 

origin of 106 

Nitrogenous manures 121 

Number of soil particles 15 

Odor of soils 42 

Organic acids, action of, upon 

soils 70-1 

Organic compounds of soil, 

classification of 86 

source of 86 

Organic nitrogen 121, 126 

Organisms, ammonia produc- 
ing 117 

of soil 117 

nitrifying 114 

products of 118 

Osborne 16 

Orthoclose 52 

Oxidation of soil 40 

Peat 127, 133 

Percolation 26 

Permanent meadows, manur- 
ing of 226 

Permeability of soils 36 



Phosphate fertilizers 164 

commercial forms 167 

manufacture of 170 

as plant food 164 

removed by crops 165 

reverted 168 

rock 169 

slag 171 

use of 171 

Phosphoric acid of commer- 

mercial fertilizers ..167 

available 164, 176 

acid in soils 166 

acid, deficiency of. . . . 210 

removal in crops 165 

testing for 271 

value of 171 

Phosphorus compounds of 

soils 61 

Physical analysis of soils ... 267 

property of soils 9 

modified by farming. . 96 

Plant food, classes of 65-6 

ash and fertilizers 216 

distribution of 78 

in soil solution • . . .66, 163 

Plants, crowding of, in seed 

bed .257 

Plowing, depth of 35 

energy required for . . 248 

fall 34 

spring 34 

influence of, on soil . . 249 
influence of moisture 

on 247 

influences nitrifica- 
tion 247 

Potash fertilizers 177 

use of 185 

of commercial fertil- 
izers 202 



INDEX 



293 



Potash in soils, sources of. - • 1 79 
and lime, joint use of • 185 

muriate of .i8r 

sulphate • •• 181 

removed in crops 177 

Potassium compounds of soil. 64 

Potato, fertilizers for 223 

food requirements of. 223 
soils 17 

Preliminary trials, with fer- 
tilizers 208 

Pulverizing soils 249 

Questions 275 

Rainfall and crop produc- 
tion 23 

Rape, food requirements of .224 
Reaction of soils, determina- 
tion of 268 

References 284-7 

Relation of crop and soil 

type 258 

Reverted phosphoric acid ... 168 

Review questions 275-283 

Roberts 36, 146, 248 

Rock disintegration 45, 55 

Rocks, composition of 51, 56 

properties of 268 

Rolling of soils 33, 249 

Roots, action on soil.. -214, 233 
Root crops, fertilizers for . . .224 

Rotation of crops 230-7 

principals involved . . .231 

length of 236 

problems 237 

and farm labor 234 

and humiis 232 

and insects 236 

and soil nitrogen 233 



Rotation and soil water . ■ • 234 
and weeds 236 

Salt as a fertilizer 193 

Sand, grades of ti, 13 

Seaweeds as fertilizers 194 

Sedentary soils 50 

Seed, amount of per acre . . 257 

Seed bed, preparation of 247 

Seed residues 125 

Sheep manure 142 

Silicon and silicates 59-60 

Silt particles.. 12 

Size of soil particles 11 

Skeleton of soils i r 

Small manure piles 153 

Sodium compounds of soils. 65 

Soil, composition of 80-1 

conservation of fertil- 
ity . 241 

exhaustion 230, 259 

management 758 

particles, study of. . • • 268 

solution of 65, 163 

types 17 

Soils and agriculture, rela- 
tion of 260 

crops suitable for 258 

Soot 193 

Specific gravity of soil 11 

Spring plowing 34 

Stassfurt salts 180 

Stockbridge n, 23 

Stock farming and fertility . • 243 

Storer 60, 123 

Strand's plant ash 194 

Street sweepings i94 

Stutzer 126 

Sub-soiling • 33 

Sugar beets, fertilizers for • . • 223 
beet soils 19 



294 



INDEX 



Sugar beets and farm man- 
ures 155 

Sulphate of potash 181 

Sulphur compounds of soil • • 60 

Superphosphates 169 

Surface sub-soil, mixing of • .251 

Tankage 123 

Taste of soils 42 

Temperature of soils 39 

Tests with fertilizers 208 

Thaer, work of 3 

Tobacco, manuring of 155 

Tobacco stems 184 

Transported soils 50 

Truck farming and fertiliz- 
ers 226 

Turnips, fertilizers for.. 214, 224 

Ville loi 

Volcanic soils 51 

Volume of soils 10 

Voorhees 204, 226 

Washing of land 255 

Water, action of, upon rocks 

and soils 46 

in rock decay 48 

bottom 23 

capillary 24 

capillary conservation 
of 29-30-1 



Water holding capacity of 

soils 263 

hydroscopic 26 

losses by evaporation . 27 
losses by transpiration 28 

of soil 23, 28 

of soil influenced 

by drainage .... 28 
forest regions 29 
manures .... 37 
mulching • . • 35 
plowing .... 34 

rolling 33 

sub-soiling . . 33 

required by crops 22 

soluble matter of soils. 163 

Warington 113, 115, 116 

Weeds, cultivation to de- 
stroy 251 

fertility in 194 

Weight of soils 9 

how determined 265 

Wheat, fertilizers for 213 

food requirements of. . 219 

soils 20-1 

Whitney 15, 44 

Wilfarth 104 

Wind as agent in soil forma- 
tion 51 

Wood ashes 182 

Wool waste 126, 194 

Zeolites 53, 160 



CORRECTIONS 

Page 7, line 2, "of Liebig's" not "at Liebig." 

Page 22, line 16, "there are" not "they are." 

Page 75, page heading, "Silt Analysis" read "Soil Analysis." 

Page 94, lines 14 and 15, "humus" not "humis." 

Page 105, line 12, "propagated" not "propogated." 

Page 107, line 6, "insoluble" not "insoluable." 

Page 160, line 9, "instead" not "instread." 

Page 172, line 23, "guano is" not "guano and is." 

Page 172, line 29, "is now found" not "are now found." 

Page 181, line 26, "Peaty lands" not "party lands." 

Page 183, page heading, "Wool Ashes" read "Wood Ashes." 

Page 191, line 11, "acid soils" not "acid sods." 

Page 138, line 25, "manurial" not "manural.,' 

Page 72, reference 27 read "86." 

Page 88, reference 29 read "18." 

Page 97, reference 16 read "17." 

Page 181, reference 93 read "92." 

Page 192, reference 21 read "22." 

Page 192, reference 5 read "89." 



Specifications 

of the P\alDlica.tiorLS of the 

Chemical Publishing Co, 

Easton, Pa. 



CJJJi Net Price 

^5^ Postpaid 

BENEDICT — Elementary Organic Analysis $LOO 

Small 8VO. Pages VI + 82. 15 illustrations. 

BERGEY — Handbook of Practical Hygiene . . L50 

Small 8V0. Pages V + 1 64. 

BILTZ — The Practical Methods of Determining Molecular 

Weights. Translated by Jones .... 2.00 
Small 8V0. Pages Vlll + 245. 44 illustrations. 

BOLTON — History of the Thermometer . . . LOO 

1 2mo. 96 pages. 6 illustrations. 

COLBY — Review and Text of the American Standard Speci- 

fications for Steel l.iO 

Small i2mo. 103 pages. 2 illustrations. 

HANTZSCH— Elements of Stereo Chemistry. Translated 

by Wolf 1.50 

i2mo. Pages Vlll + 206. 26 figures. 

HARDY — Elements of Analytical Geometry . . 2.00 

8V0. IV + 565. 165 figures. 

Infinitesimals and Limits .20 

Small i2mo. Paper. 22 pages. 6 figures. 

HART — Chemistry for Beginners. Small i2mo. 

Vol. 1. Inorganic. Pages Vlll + 188. 55 illustrations 

and 2 plates LOO 

Vol.2. Pages IV + 98. 11 illustrations . .50 

Vol. 3. Experiments. Separately. Pages 60 . .25 



JONES — The Freezing Point, Boiling Point and Conductivity 

Methods .75 

izmo. Pages VII + 64. i4 Illustrations. 

LANDOLT — The Optical Rotating Power of Organic Sub- 
stances and Its Practical Applications . . . 7.50 
8VO. Pages XXI + rsi- 85 illustrations. 

LANGENBEICK — The Chemistry of Pottery . 2 .OO 

Small i2mo. Pages VIII + 19^. Illustrated. 

LONG — A Text Eook of Urine Analysis . L50 

Small 8V0. Pages V + 249. 31 Illustrations. 

MASON — Notes on Qualitative Analysis . . . .SO 

Small 1 2mo. 56 pages. 

MEADE — The Chemical and Physical Examination of Port- 
land Cement LOO 

MOISS AN — The Electric Furnace 2.50 

8V0. Pages 10 + 505. Illustrated. 

NOYES — Organic Chemistry for the Laboratory . . 1.50 

Small 1 2mo. Pages XII + 25?. 22 Illustrations. 

PHILLIPS — Methods for the Analysis of Ores, Pig Iron and 

J'teel. Second edition LOO 

8V0. Pages VIII + 1 to. 3 illustrations. 

SE.GE,R — Collected Writings of Herman August Seger 
(Papers on Manufacture of Pottery.) 
2 vols. Large svo. $ 1 5.00 per set. $r-50 per volume. 

SNYDER — The Chemistry of Soils and Fertilizers . L50 

New edition in Press. 

STILLMAN — Engineering Chemistry . . . 4.50 

New edition in press. 



VE,NABLE — The Development of the Periodic Law . 2.50 

Small 1 2mo. Pages VIll + 52 1 . Illustrated. 

The Study of the Atom 2.00 

1 2mo. Pages VI + 290. 

V ENABLE CH HOWE, — Inorganic Chemistry According 

to the Periodic Law 1.5 O 

i2mo. Pages VI + 266. 55 illustrations. 

WILEY — Principles and Practice of Agricultural Chemical 
Analysis 

5 vols. 8VO. New edition in preparation. 

Monog'raplns on 

Applied Electrochemistry 

^^m^^ Net Price 

• ■ Postpaid 

ENGELH ARDT — The Electrolysis of Water . $1.25 

8V0. Pages X+140. 90 illustrations. 

LeiBLANC — The Production of Chromium and Its Com- 
pounds by the Aid of the Electric Current 1.25 
8V0. 122 Pages. 

NISSENSON— The Arrangements of Electrolytic Laboratories 1.25 
8V0. In the press. 

Others in Preparation 



MEADE — Chemists' Pocket Manual .... 2.00 

i6mo. Leather. Pages VII + 204. 

TOWER — The Conductivity of Liquids 
8V0. In press. 



The Study of the Atom 



or 



The Foundations of Chemistry 

By 
F, p. Venable, Ph.D., D.Sc, LL.D., 

University of North Carolina. 



CONTRNTS. 

Chapter I — Ancient Views as to the Nature of Matter. 
Chapter II — From the Greek Philosophers to Dalton. Chapter 
III— The Atomic Theory of Chemistry. Chapter IV— The Re- 
lative Weights of the Atoms. Chapter V — The Periodic or Natu- 
ral System. Chapter VI — AfHnity, the Atomic Binding Force. 
Chapter VII— Valence. Chapter VIII— INIolecuks and the 
Constitution of Matter. 

vi+290 pp. bound in cloth. Price $2.00 net post-paid. 



The Chemical Publishing Co. 

Easton, Penna, 



Monographs on Applied Electrochemistry. Vol. 111. 

The Production of Chromium 

and its Compounds by 

Aid of the Electric 

Current 

By Dr. MAX LE BLANC, 

Professor and Director of the Physical-Chemical {Electrochemi- 
cal) I nstitute of the Technical High School, Karlsruhe 



Authorized English Translation by 

Joseph W, Richards, M.A., A.C., Ph.D. 

Past-President of the American Electro- 
chemical Society. Professor of Metall- 
urgy at Lehigh University : : : 



CONTENTS. 

I. Obtaining OF IVIp:tai.lic Chrc mium. {a) By the Electro- 

lysis of Aqueous Solutions; ((^) At High Temperatures. 

II. Obtaining of Compounds of Chromium with Metals 

[a) By Electrolysis of Aqueous Solutions; (d) At High Tem- 
peratures. 

III. Obtaining of Compounds of Chromium with Non- 
metaLS. {a) Carbon Compounds; {d) Silicon Compounds ; 
(c) Phosphorus Compounds; {d) Sulphur Compounds; (<?) 
Oxygen Compounds. 

(i) Chromous Compounds ; (2) Chromic Compounds. 

(a) By Electrolysis of Aqueous Solutions ; ((^) At High 
Temperatures. 
(3) Chromic Acid Compounds. 

{a) Chromates of the Heavy Metals; (b) Chromates of 
Alkalies and Chromic Acid. 
viii+ 125 pp. Price, net, post-paid. Paper, $1.00. Cloth, |i. 25. 



AUG 15 1905. 



LIBRARY OF CONGRESS 



0002^(335111 



